I will admit that sometimes I get tired of the "5E is broken because ..." threads and could have stated my question more clearly.
How about this: what's wrong with the Champion fighter and why does it need to be changed? Why not just play one of the other variants?
So let's talk about some of your concerns.
Well the problem that I am personally having (not speaking for anyone else in this thread) is that the Champion and Battle Master are just representations of the 2E and 4E Fighters respectively. It seems they entirely left out the 3E Fighter gameplay style. Where you had always available combat options by having a bunch of combat feats to tailor your Fighter. I would love a Champion style fighter (no to little resource management) but with decisions to actually make in combat.
What can I say? I guess I simply disagree with a caveat. Builds in 5E are quite front loaded, in some ways even more so than previous editions.
But flexibility? Hmm...well backgrounds can give me things that aren't typical fighter. Party doesn't have a rogue? Get lockpicking from a background.
Then you have the basic choices: strength vs dex, melee vs range, shield or no shield. Heck, I've seen a fighter that was mostly wisdom based that took a feat so he could use shillellegh to be effective in combat (he later multiclassed into cleric).
We have less "feat tax" in 5E than in 3.5 and feats are more significant. So do we have less feats? Yes. But I also don't feel compelled to take expertise or specialization just to do what should have been given to me as part of my class.
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This is all reinforced by Mike Mearls himself from the Tome Show interview below:
https://merricb.com/2015/08/02/mike-mearls-speaks-tome-show-interview/.
My takeaway from the interview was not that he was dissapointed in the fighter classes, but that he thought they could have come up with a better more evocative name.
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This is all ignoring the fact that the Champion is mechanically sub par at the only thing it can actually do, damage. I don't think Wizards did that on purpose and I'm assuming the Champion was created during the playtest when critical hits were max damage plus extra damage die and were never looked at again when the rule was changed.
I'll be honest that I don't really care too much about DPR. The analysis that I've skimmed suggests that the difference is minimal, varies by level, feats and ultimately amounts to a point or two of damage while getting better defenses. Crunch the numbers in slightly different ways and you get different answers.
If you want to get more damage you could always do a dex based champion and throw in a few levels of rogue. The sneak attack damage dice get doubled with crits, which you'll be doing more often as a champion.
NOTE: I'm sure there's something that doesn't work with this build that would still fall a point or two behind some other build or otherwise break down. I don't care enough to come up with a better example.
I do sometimes miss Brogg the 3.5 chain fighter who took a couple of levels of cleric so that he could enlarge himself and knock down most enemies on the board. But I'm sure if I wanted to I could make something equally cheesy with a reach weapon and a feat or two.
So to have a real discussion about this you'd have to go deep into the math, come up with examples and counter examples, build vs build. While you're at it, throw in some playtests so a few thousand people can kick around your ideas.
I think that the very fact that WOTC hasn't released much in the way of a new type of fighter in published materials or unearthed arcana suggests that most people like the champion fighter just fine.
And if you don't like the champion, there are plenty of other options.