I am starting to seriously wonder if you actually play the game, or if you just white room theorize almost all of your experience with it.
There's nothing shameful in admitting you're wrong, Mistwell, no need to deflect with false accusation, however irrelevant. ('White room theory' is verifiable fact, it's based on the game's actual rules - anecdotes aren't verifiable, vague sweeping summations of decades of experience aren't fact - I could provide plenty of both, after 37 years of gaming, but I'd rather stick to facts we all have ready access to. Fire up the SRD and confirm what I posted, above, look up some of the optimal builds on-line, I suspect I only touched on a fraction of what they can do.)
You said that Whirlwind Attack was still in the game because the fighter could, at his best moment, at relatively high level, come up with 6-8 attacks. I just pointed out that doesn't hold a candle to the crazieness you could pull of in 3.x with WWA. WWA was essentially an area attack, so the upper limit was how many enemies you could get in one place - not even one terribly small place.
Conversely, if you faced a single foe WWA was meaningless, while the 3-attack 5e fighter will be beat him down, very effectively (not that there isn't a 3.x build for that, too, but it's not a quality of WWA). The 3.x fighter might WWA two or three times in a row, even, against moderately tougher opponents, not because that's as good as focus fire, but because it was a better option for him, given that ability - even sub-optimal, it's a bit defining, and quite different from simply getting Extra Attacks, undeniably potent though they may be.
WWA didn't make it into 5e.
Clear?
I'm pretty sure Tony does play quite a bit
Thanks for that, I do, not as much as the 30hrs/wk I did back in the day, just a couple hours every Wed and a 1/mo home game - I've even missed the last two conventions I normally attend. But a whole lot over the last 37 years. I just don't feel that has any bearing on whether WWA is in 5e or not.
, but I think there's some confirmation bias going on here. I see people playing fighters all the time who are perfectly happy with them.
Tons of confirmation bias! For instance, deeply analyzing the rules might not confirm that fighters are just fine as is, but noticing any time someone playing a fighter has a good time can confirm it handily and repeatedly.
That's not to say I'm-immune-and-you're-suffering, it's just that it's a very human, positively pervasive thing. And assuming every good point someone else makes is their confirmation bias, can be confirmation bias, on our part, as well...
That's a perk of 'theorycrafting,' it scrubs /some/ (not nearly enough) of that off by being verifiable.
This might be the first time in 17 years that I've thought someone genuinely doesn't grok D&D and maybe shouldn't be playing it. People say there is no such thing as badwrongfun, but laughing and being condescending to people more creative than you because they are more creative than you and don't view D&D as a game you win is in fact badwrongfun.
"Choose your enemies carefully, for it is they you will come most to resemble."
This is true. Its fine to be an optimizer but its not what the game is about. That's the whole idea behind bounded accuracy. The purpose of bounded accuracy to give flexibility to builds but not penalizing them, although some players clearly don't get that.
More broadly, it's the point of game balance, in general, keeping all the choices presented 'viable,' even in the face of applied system mastery. But simply designing options within narrower limits can serve the same purpose, it just means presenting fewer choices in the first place.
BA does mean that every bonus is gold, the optimizers' aren't wrong about that. But it also means that lacking a bit of gold doesn't leave you non-viable - the d20 will still make up the difference much of the time.
There is a player out there with a thread that is playing a low INT wizard to test his knowledge of the rules and see if it is even possible.
Works surprisingly well.

There's spells that just don't key off INT, you loose a certain amount of versatility, both from knowing fewer spells and choosing from a narrow list of viable ones, but the wizard has a lot of versatility to lose.