You folks (not just the ones quoted here, but others as well) talk about "good" and "best" as if they are some objectively definable things that everyone else should also respond to - as if you all actually agreed about what those things were.
You talk like "favorite" isn't something determined by more factors than just the system. And that, if you'd have your druthers, you'd only ever consume your one favorite food, watch your one favorite show exclusively - and that if it isn't your favorite, it can't be totally awesome anyway.
You talk like this is still the 80s, and finding out about other games is still hard, and that the small game companies aren't currently experiencing a renaissance of kickstarter products and players for those products like never before.
You folks look to be going to significant rhetorical effort to deny, reject, downplay, discredit, or deflect the idea that D&D... might actually be a good game.
I find that interesting.
It is interesting, isn't it? But so is the fact that you're putting words into people's mouths in precisely the way you yourself have correctly criticised and even had to moderate others doing. You're telling us how we think and what we think, and putting words directly into our mouths. Plus you're grouping together people with disparate opinions, which is, y'know, kinda rude.
And then the second-last line undermines the whole thing - if it's all relative, as your first line proposes, why does it matter? How could a game even be "good"? You can't have both, that's just shenanigans.
Personally, when I say whether a TT RPG is good, I'm largely talking about the mechanics, but also the presentation, and the way the mechanics influence other factors - often via the presentation to create stuff like how accessible it is. We've all seen relatively simple RPGs presented in ways that made them seem complex and difficult, or relatively complex RPGs presented in simple and accessible ways that made them more playable than they could otherwise have been.
If I take the words you've shoved in my mouth out, I
would actually say D&D 5E is in my list of "good" RPGs, it's just not quite in my list of "great" ones, because it's a fundamentally a compromised game, a three-quarter measure. It was designed as an apology to fans, and it's success was not expected, nor designed for - some elements of 5E, as have been discussed in entire threads before, seem to owe a lot more to "OMG what will win grogs back from Pathfinder?!" rather than "What will make 5E an amazing game with massive accessibility?".
To me, as a compromised-but-modern design, 5E is quite impressive. More importantly, it has a ton of support. This is something that matters to what you actually play quite a lot I think, unless you're playing in a very self-contained way. But that doesn't make the
RPG itself good in the way I mean it. It makes the support good. I mean, if we look at multi-player computer game, we can see a comparison - a lot of pretty mediocre multi-player games are pretty successful more through inertia and support and size of audience than quality of game. This isn't just a snobby thing, if anyone wants to claim that, I'm waaaaaaaaaaaaaaaaaaaaaay too old to fall for that nonsense. I've seen games rise and fall. I've seen games go from being hot, to not. And I've seen that that doesn't correlate extremely well with positive quality. Actually-bad or subpar games die fast, but 7/10 games? If they land at the right time, get enough players? They can go forever - and someone releasing an 8/10 or even a 9/10 game in a similar genre? Probably not going to have much impact. God help you trying to stop even an 8/10 game that has a big enough audience behind it, like WoW. Like train schoolbus gif man.
And I feel that's what 5E basically is. A 7/10 RPG with 11/10 support (no-one could match WotC's support - and the support the sheer popularity of the game creates with third parties). Does mean I should see it as like an 18/20 game? Maybe. I don't though.
I think your point about the '80s is interesting, I wasn't really around much then, but I don't think things have changed as much as you're trying to imply, because getting a group to try other games isn't merely a matter of getting hold of those games. I was lucky perhaps when I started playing RPGs, because I never really any difficulty getting hold of RPGs. I had enough money (between me and my brother and perhaps excessive pocket money as kids, initially, and then odd jobs and so on when older, until employment), and living in London, pretty much any RPG I could hear about, I could get, as the shelf behind me attests. The difficulty is transitioning players into playing it. Especially if the character creation is
at all complex. As such, in the modern era, I've had a lot of success with PtbA/BitD-based games, Resistance-system games and the like (I suspect SWADE could also work, haven't tried it with my group yet), but am I ever going to run Cyberpunk Red or the Age of Sigmar RPG in their own systems? I very much doubt it (even though AoS is kind of simple enough). I think it's actually a lot harder, now, to convince a group to try a new system than it was in the 1990s. Is that because most gamers I know are 35-45? Maybe, but I don't think it's just that.
One thing that really helps D&D with my group is D&D Beyond. If it wasn't for D&D Beyond, there's no way we'd be playing 5E. Combine with the fact that a couple of the players just aren't very good at engaging with new systems, that 5E is at least a B+ game (7/10 being at least B+ in most grading systems I'm familiar with), and that 5E has staggering amounts of material for it, and you've got a pretty good reason to run D&D. Again maybe for you, a really decent solid game with amazing support is actually an amazing game. That seems to be what you're getting at. But that's not how I see it.
At it's heart, 5E is a compromised 3/4-arsed design, with a lot of weirdly clunky stuff and some sad attempts to shove 4E's prestige'd corpse under a bed (the feet are quite clearly sticking out), that's way more compromised and confused than is normal in actually-new RPGs. That's why I don't think it's great.
If you do a more generous comparison, maybe, don't compare it to it's contemporaries, but games from the '00s and earlier, and 5E looks absolutely great. Had 5E come out in 1994, it'd have been a 9/10 game, only losing that point for poor resolution system for out-of-combat stuff.
Let me just add - I think if they have the same attitude they seem to have NOW in 2021, rather than the "I've made a terrible mistake" of the 4E/Next era, 6E will be a genuine 10/10 RPG which I will not be able to look down my glasses at.* They have the money, they have or have access to the talent, they have the audience to test it with, they should be able to make a staggeringly good RPG.
* = I don't actually wear glasses, so this is entirely metaphorical.