I don't think this is necessarily bad. Compared to people who only dabble in things, someone who spends a decent amount of time on something actually is "pretty good" at it even though they might not be top tier to people within that same culture.
I think there is some popular (dan luu?) blog about this. You can actually pretty easily be in the top 1% of skill or knowledge on something, and while that doesn't make you a world expert by any means, it does kinda make you an expert to an average person. My 1600 rating is very good within the pool of people who know what chess is and can play it, even though it's not impressive at all for people who actively play chess.
Also, most people who are good at something let their actions speak.
The difference between good and mediocre is significant. To the point that I cannot return a good tennis player’s serves. The difference between mediocre and post beginner is just as significant.
Two nice things about golf - the handicap system let's two players of different level engage in fun competition. (Yes, handicaps can be manipulated, but for the most part aren't. )
Second a very good player can play with a bad player, and both can have fun. The social factor is more important to the fun, and I've enjoyed tight games with people with hugely disparate handicaps.
With tennis I always want to play either someone just a little bit better than me. Someone who can help me get a bit better all the time. My enjoyment of the game depends a lot on their performance.
Both are enjoyable in their own right.
I only experienced something like this once, late 90s. We thought of ourselves as pretty ok StarCraft players until we got some visitor to a lan party who basically demolished everyone. This was pre-ladder iirc so you only played a handful of games online.
Tennis of course is harder. You can only be as good as the people you are playing with.
That’s the appeal of Dunning-Krueger. It’s become a blanket label for every moment of ignorance or confident stupidity someone sees in others.