But if the OP is talking about the US, there's that whole other dynamic mentioned in the sibling comment.
You: hej må jeg have... et varm chokolade?
Them: of course, will there be anything else?
You: hvis det er okay jeg ville gerne øve mig på dansk *smile* åbenbart har jeg virkelig brug for det
Them: selvfølgelig! det kommer til... fem-og-halvfems kroner. Sidder i ind, eller ude?
If you don't explicitly say that you are trying to practise then yeah, they are going to default to whatever makes the interaction go smoother. Everyone does that, all the time! But people are generally pretty supportive of another person trying to learn. And of course, people aren't going to assume you think they can't speak english if you say you're practicing (it's not hard to smile and say how lovely you think the language is or whatever.
In general waitstaff and service workers deal with people being indecisive, slow, speaking with confusing dialects, speech impediments all day long. It is not an imposition to work through an imperfect language - and its pretty much the only way anyone ever gets good at a language.
I also get the impulse to be a little jealous of those natural born sunny extroverts who find it easy to do this. For me it does require pushing through a little discomfort, and often I wouldn't if I were busy doing something else. But it's 100% my own discomfort, not the other person. Being asked to hold a conversation in your own native language is not a chore
You may tell the Danish cafe staff that you need Danish and you want to practice, but that poor person is an employee and hardly in a position to tell you what they really think.
I also know Danish people who prefer to speak in english. If I were speaking to them for hours at a party, and they voiced that request, I would oblige. But avoiding trying to speak danish in denmark because of the fear some danish people would be annoyed or even offended without ever asking them is utter insanity.
You say you have travelled the world for language practise, but how did you manage that if you refused to speak the language for fear of somehow offending or inconveniencing people by speaking in their language. Why was it any different from just staying home and reading websites in your target language?
I travel the world for language practice and don't feel too embarassed because 1) I try to get to a B1 level before talking, and 2) I travel in a way that brings me into contact with a lot of elderly people happy for any social contact and novelty. But I am definitely aware of the need to avoid inconveniencing younger people.
Your expectation, imposed upon yourself. I get it, I was embarassed too. It's really not that serious, you can be bad at stuff publicly. Nobody is advocating following people around forcing them to teach you something, but you can still have a great time with people with whom share no language in common. Speaking anything at all just makes things more fun, and people are way more willing to help than you think.
It's just not rude to go to a foreign country armed only with a1 duolingo and a prayer. It's a lot less rude than going there and only speaking english to everyone you meet... Yes even in denmark, even to young people.
As I have gotten better at danish I have had many more young people (the majority of my friend group and social experienced given I went to university here) express that they would prefer to speak to me in danish than the other way around. They were, by default, always making themselves a little uncomfortable, feel a little slower, seem less educated for the sake of communicating with me, because I gave them no other option. Now that I give them the option of switching to a context where I seem like a fool and they are the master, they are happy to take it.
Younger Europeans do not necessarily see it as rude for a foreign visitor to come and speak only English. Many local younger people spend a significant portion of their lives in an English-language environment on social media, and mixed European marriages now often use English as the home language. English is no longer seen as an outside thing by which foreigners speaking it are being rude and unappreciative.
And again, domain loss is already ongoing for European languages (and for the Nordic languages this has been observed for like decades now), so it isn't necessarily the case that locals feel more proficient about certain things in their native language and less proficient in English. I have colleagues who would prefer to speak English about technical matters for their own sake, not mine.
I can't emphasise enough that I am not only literally a young european, living with a young european partner, with a young european social circle, but I also exist in the real world and not in reddit. I have lived here in denmark for coming up on 10 years.
Yes, I know some extremely online people who have learned better english than danish and talk about noticing a decline in their danish skills. Those few who spend all their time online, on reddit and the like. It's definitely a type, one that by my estimation skews male, autistic, and introverted. Prime hacker news demographic type thing :)
I get it, for you as a linguist its remarkable that this could happen, that people could exist that lose their native tongue or learn another to a higher proficiency of that of the country they live in. We do live in unprecedented times.
However I do not think it is universal, or a majority of young people - I also know many more people who have better knowledge in Danish than in english. It is explicitly on issues of politics, business, science, law, etc that people prefer to speak in danish with me because they do not know the words in english, including at meetup groups dedicated to those things.
1) For some years now, restaurant wait staff in several large European cities, including my former hometown, often only speak English; you simply can't order in the local language. I am basically the only person who complains about this; my peers who are locals don't bat an eye, they don't see it as offensive at all because English is so normal for them.
2) I have a longtime asssociation with one of those Southeastern European countries known as an emigrant factory. My friends who left to Northern or Central Europe or the Baltics have relatively little interest in using the local language except where (like in Germany) required for interacting with bureaucracy. They feel fine living in English. Back in that country, it has not been unusual for the last decade-plus to hear younger people speaking to each other a mixture of English and the local language, and foreigners moving there now complain they get little opportunity to immerse in the local language as I once did.
3) Themes of anti-globalization and protection of European cultural and linguistic diversity have increasingly become associated with the far-right (a quarter-century ago, this was a passion of the left in some countries!). As is known, the far-right is a vocal force but a minority everywhere.
as for 2, yes young people sometimes speak to each other in a mix of english and danish. It's using danish grammar, and critically, not english. You couldn't follow at all if you only spoke english (and with significant difficulty if you only spoke danish for that matter). I consider this similar to the process that creates slang
the other part of 2 regarding people that don't rush to learn the local language. Yes I know people who do this. After living here long enough, especially if they plan to stay, they tend to change their tune. I think there is a lot of motivated reasoning on this topic in particular, including stuff I have said to people myself in the past that friends like to remind me of - Whne I first came here I literally used to talk about how its so hard to practise language because locals won't help while being surrounded by locals who are happy to help. I won't speculate as to why people change after staying somewhere long, its just a tendency I have seen.
regarding 3, it is seemingly often associated with the far right yes, especially when bound with nationalism and themes of invasion/protection, but not unique to those contexts. I have experienced this in leftist political spaces personally, up to the point of votes being held and passing, restricting language in spoken meetings to danish only, explicitly for the comfort of those attending. And of course, I have also experienced this in entirely unpolitical spaces like hobby clubs, discussions at parties, and at work.
You can try to order the food in local language. And if they respond in English, you switch to English (if you know it), it is not an insult nor situation you should overthink.
You do not have to assume the worst possible attitudes just because someone is young. Yes, some do dislike foreigners in principle, but that applies no matter which language you use.
Not sure why you think B2 is useless for ordering food. B2 is the level at which one can work in an office environment in the local language, it is already beyond ordering food.
Also, I had to explain those labels to Europeans enough times to think the labels are not known by random people.