> If I don’t hear back from you in [N] days, I am not going to do XYZ, considering you don't deem it to be important.
Sounds even more confrontational.
Sounds even more confrontational.
> I'm going to proceed with XYZ in N days. If any of you fucking idiots have a problem with that, then scrawl it down in crayon and flush it down the jacks, which is where you'll end up if you dare question my decisions in future.
Though I’d tone down the swearing
In that case, the most likely mismatch between the language you provided and the responses you're getting is your use of the word "considering".
If you're using it to describe the state of mind you'll be in after you fail to receive a reply, that was a mistake. It is a common connective in English that explains the reason for something:
https://www.merriam-webster.com/dictionary/considering
https://en.wiktionary.org/wiki/considering#Preposition (the preposition)
What this means is that the sentence "I will go ahead with changing X, considering you don't think it's important" is equivalent to "I've noticed that you don't think X is important, so I'm not looking for your input on my proposed change".
Learning a language well is a double-edged sword - if you look like you know what you're saying, and you make a mistake, people will assume you meant what you said. You can get away with really outrageous things if you come off as someone who can barely talk. But long after that point, there will still always be things that you never quite learned.
Maybe they were sick for a couple days. Or were recently on vacation (and you haven't been notified yet). Or dealing with some higher priority emergency. Or just genuinely missed the email for some reason (accidentally sent to spam folder?)
Also even if it is true that the recipient thinks it is unimportant, it doesn't follow that the thing should be done. If somebody sends me an email asking me whether they should swallow bubblegum (or something on that level of trivial stupidity), I'd think they shouldn't -- but probably wouldn't bother to respond, or at least I wouldn't write a lengthy email explaining why not.
I'm not even joking, these days I often scroll through social media with a mild kind of twisted amusement watching people do and believe in stupid things -- while I can reply to each of them explaining why they're wrong, it's a well-known fallacy due to xkcd386. Coworkers are admittedly "closer" and thus I probably should warn them about potential hazards, but if it's a large org and I was just among a long list of cc-ed people... I might decide not to bother.