I don't care about something I don't actually believe, lol.
It's been mentioned multiple times now: casters are not good until high levels. Even then it's mostly access to high level wizard spells that leads to the caster biases.
Limited spell slots whiffing on low DC's is more restricting than some people seem to realize.
When spell casters have a lot of spell slots and have many spells prepared and have a higher DC and access to higher level spells they can do quite a bit, but that isn't all the time through all the levels or with all the disadvantages.
I mean, you don't have to
believe it or not. People swore up and down that non-casters weren't in any way lesser than casters in 5.0,
and yet the designers themselves later straight-up said that long-rest characters, especially casters, were outperforming non-casters in the actual feedback they were getting from real, live games. Just because it isn't a problem
for you doesn't mean it isn't a problem
for anyone.
I fundamentally disagree that casters are "not good until high levels." They require slightly more optimization effort to reach their full potential, but that in no way means they're somehow
bad until 11+ or whatever threshold you decide upon (since I find many who argue for such a threshold keep it quite...mobile, shall we say.) Wizards and Land Druids can be that good by level 6, doubly so because they have slot recovery mechanics.
Fireball (Wizard, Arid Land Druids) and
call lightning (any Druid) are great damage options, and you only need one other reliable damaging slotted spell (e.g. not cantrips) to have reliable damage output, e.g.
magic missile (Wizard) or
ice knife (Druid).
Shield gives a Wizard all the in-combat defense you could ever need, to the point that Bladesinger Wizards are some of the best tanks in the game, and while Druid doesn't have anything quite that good,
barkskin is still pretty solid. That's only three spells, and at level 6, a Wizard or Druid can prepare ten. Add in
haste or
fly for a terrifically strong buff effect (Druids would probably go with the ever-present backstop,
revivify, or a spell from their subclass). And even if you did both, you'd
still have half your prepared spells remaining.
I definitely think 10 spells prepared to spread across three spell levels--meaning you can have a distinct spell for every slot you have at 6th level!--is
plenty to be versatile and yet also very strong. You can easily have one defensive option, one offensive option, and one other/utility option per spell level, plus an extra spell to do whatever you want with. And then Wizards are kings of ritual magic (any spell you've learned that has the Ritual tag can be cast, even if you haven't prepared it), meaning they get
even more magic without needing slots to do it.
Something as simple as weapon masteries is per attack instead of per action opens up quite a bit with multiple attacks. I think casters and martials are different from instead of better or worse than.
Oh, don't get me wrong, weapon masteries are nice, especially because they're something spellcasters--even weaker ones like Warlocks--cannot get.
But I just flatly do not accept that even relatively powerful ones like Nick, Graze, or Vex are in
any way comparable even to the power of a strong 1st-level spell like
shield, silvery barbs, or
healing word, let alone 3rd or 4th level spells. Obviously, weapon mastery properties are
easier to use than these things because they just happen (though you are not quite correct, in that several of them are only 1/turn, not 1/hit, e.g. Vex, Slow, Nick, and Cleave are all once per turn). But just because it's simple doesn't mean it's stronger. Class tiers are about potential power if you optimize, not about average performance if you presume an undefined but low level of system knowledge. Spellcasters so heavily reward making "the right" decision (or at least "a very good" decision) that their power spikes pretty hard
if played to the hilt. Which...is the point of the tiers. If someone is just casually playing and doesn't really think about mechanics or optimization, then any conception of "tier list" is out the window from the get-go; you have
presumed that the player generally isn't bothering to be stronger, and thus any claim that these other things are thus stronger is circular logic.