Shardstone
Hero
Personally, I don't believe in niche protection anymore. I did for a really long time, but I think its better if the niche is based on BOTH the class and subclass, and not the class. This is precisely because of your last line about how every D&D player wants to be a QB.Wizards aren't better, it's just that better players play wizards!
That's a bold strategy, Defcon1. Let's see if it pays off for you!
Anyway, I think that we are missing two important things when it come to the question posed by @Asisreo above.
In terms of asymmetric class balance, there is one other way that should be considered-
Niche protection. One of the big issues with 5e, IMO, is that there has been a lessening of the barriers between classes. Through the feat system and the ubiquity of spellcasting, as well as the desire to harmonize DPR, there just isn't a lot to fully differentiate classes in the same way that there used to be.
To compare this to (American) football- if D&D is a team sport, you need players at different positions. You need a QB, sure, but you also need RBs, and WRs, and offensive lineman. And that's before you think about the defense.
The problem, such as it is, is that every player in D&D wants a QB. And maybe that's the best way to make the game! But it does lead to less differentiation between classes when every player wants their class to be equally good at all the things that other classes do.
However, I will point out that a big reason every player wants to be a QB is because the game has really mediocre options for being a support character. Outside of boss fights, its usually better to use spells on damage. Things like Bardic Inspiration have a lot of uses for a small pool depending on the Bard subclass. Most Channel Divinities are offensive or outside of combat utility. There isn't a varied AND strong set of options, be it in spells, classes, or magic items that lets me be like a Support in League of Legends. The closest is save or suck spells, but that's only one part of being a support.
That aside, every class should be able to at least dip its toes into every role. Like Blade Singer being a melee dodge-tank Wizard or College of the Moon being a melee tank Druid. The alternative is you end up having a situation where certain classes are necessary. You always need a druid, paladin, bard, or cleric because you need heals. You always need a fighter, barbarian, or paladin because you need someone to keep them off the "squishies." When you offload that weight into the subclasses, even just a little bit, you can have a party of all druids, all wizards, all fighters, etc. Or you can have things like Warlock (Celestial heals), Druid (Moon melee), Bard (Swords backup melee), Ranger (environmental utility magic).