He's not the only one saying that they don't see the problem at their table. Some people seem to say that every fighter out there uses this one feat and only this feat, but I've never seen it. YMMV.
Yeah, it makes so much more sense when the fighter uses his one bonus ASI at 6th level for GWM/SS when he's behind on damage, for Actor when he's behind in the Social Pillar, or to shore up a low stat when he's suffering from bad saves, etc, etc, etc....
That's kind of he point.. many people used to say quadratic wizards were not a problem at their tables. We all now ageee such a thing is problematic and such people were either naive or blinded.
Except for the people still saying it, of course. And, seriously, there are players/campaigns for which LFQW if still a feature, not a bug.
Why those feats are optional if they are mandatory to Classes balance?
Because class balance is optional.
If, for some reason, you want class balance, and want to
play run D&D, anyway, you can opt into it. You choose a specific sub-set of the rules that you find least imbalanced or most susceptible to being balanced, run your campaign in 6-8 encounter/2-3 short rest 'days,' place a variety of challenges that puts each PC in the spotlight, in turn, place magic items and any other perks with an eye towards maintaining or re-establishing that balance, etc...