Don't mind at all, even if it were actually limiting people to 480p entirely (which doesn't appear to be the case, just changing the default option which is even less of a big deal, but even if that were what it did, I still wouldn't mind much). It's for a good reason, and when I'm watching stuff like YouTube and Twitch and the like, I usually watch at 480p anyway. Because like my Internet is okay and stuff, but when I'm watching that stuff these days, a lot of time I have like two things open. Like right now for instance, I'm watching like Keizaron on Twitch on my laptop's monitor and Spikevegeta on my other monitor. And like I said, while I have decent Internet and it's probably fine, nonetheless streaming both of those things in HD, especially at the same time everyone else in my family might also be using the Internet for various things... That might also be fine usually, but I don't like to push it at all, so I usually have everything in 480p anyway because it's just what I'm used to and I legitimately don't mind.
But even if that weren't the case, even if that weren't something I was already used it, it's for a good reason, so whatever. And unlike something like Netflix, YouTube is free to begin with (I mean, there is a paid YouTube service, but that has to do with stuff like ads and some other stuff, and nothing to do with quality or anything, IIRC), so yeah, definitely don't mind at all, in any way.