There are some heavily generous presumptions going on in those claims you’re tossing in off the cuff.
First, the “unless it wasn’t going to be fine anyway”. That’s not how those 2 work - the benefits Lust and Bres bring can essentially remove that possibility entirely. A Lust on an encounter like Cragmaw, or Talondrus, can effectively remove the hardest part of the encounter. Even in raw numbers, Lust and Bres when they’re used can effectively add/remove multiple minutes worth of forgiveness into the dungeon, even in a +12, or +17. Even if a group is going to make the timer with, say, 30 seconds to spare without Heroism or Bres, the added time saved or forgiveness, has a non-negligible impact on how you can approach the most difficult pulls in the instance, whether you feel like you need to take a risk at a certain point, how much you need to optimise in a certain point of time, etc. Your premise is disingenuous.
Then on top of that, the vast majority of us is doing some lifting. Who’s “us”? Is this including you and me? We can probably roll up into +15’s or something blindfolded and be fine, but that certainly doesn’t represent or mean anything about other people in the PuG scene.
Ultimately, you’re circling back to the same framing of pitting class considerations with personal improvement as if they’re mutually exclusive. They’re not, of course. People can bring the Lust healer, or the Brez healer, whatever, and help themselves play better.
One could even make the argument that learning how to optimise your play with Lust, especially so for specs whose cooldowns or abilities change during Lust, or learning to be effective using Brez (as opposed to wasting Brez) is itself a skill that’s part of “playing better”.
That’s a dishonest representation of what was going on when Feral was unpopular. It’s not like Feral was suboptimal at +32, but the community didn’t realise they were really good actually at +12. The community’s response was in reaction to Feral’s numbers and toolkit being in an objectively bad place, especially in comparison to Boomkin. They could play with Ferals and see them doing lower numbers than an even worse Havoc DH or whatever. The few veteran Ferals who are good, and could keep up, doesn’t even negate those experiences for the rest of the playerbase.
We’ve extremely rarely come across situations where classes are good actually, but they’re perceived poorly by the community. Those examples would be actual community issues.
Those are not the thing you’re debating. It’s not like people are in the spot where Hero is actually outshined by, idk, Mistweavers at +12. No, Mistweavers are in a bad place, Hero is good actually, Resto Shaman brings a lot of other good things and is therefore Meta, while Mistweaver is sitting at D-tier, so people in +12 will go “Yes, gimme that Resto SHaman”*. Throwing in hypotheticals about class not being effective in a +27 but could be a top performer in a +17 to situations where it’s not even applicable is just sidestepping the convo.
*Excepting the situation of healer shortage and accepting the inferior option out of desperation.