So the question is: what specifically can D&D 5E do to fix this problem?
I'm not sure what you mean by a 'plus thread' and I'm 20 pages late but anyway, for me a big problem is that the Fighter isn't actually very good at fighting, both offensively and defensively, and you have to use Action Surge for combat instead of one of its many non-combat uses. Fighters also pall in comparison to Paladins (thanks to additional Radiant damage) & Rangers (thanks to persistent Hunters' Mark & other effects) in Tier 3 in general combat.
Fixes:
1st level - Defensive Bonus: Your base Armour Class can become 10 + Armour + Defensive Bonus. Your Defensive Bonus is the lower of your Proficiency Bonus and your levels in the Fighter class and is limited by armour as your Dex bonus is (e.g. max of +2 with Medium Armour). You may add to your AC with a shield, Fighting Styles, magic, and the like. Your Defensive Bonus may not be used with Unarmoured Defence.
2nd level - Action Surge - Fighters get non-Attack Action Surges equal to the lower of their levels in the Fighter class and their Proficiency Bonus to take Actions that cannot be used for attacks (q.v. Rogue's Cunning Action). Fighters also get Action Surges that can be used for attacks at 2nd and 13th levels.
4th level - Indomitable gets brought forward to 4th level and becomes an auto-save, like Legendary Resistance except it also works on no-save situations. You get additional uses at 9th and 17th levels.
5th level - Consistent Attack: when you take an action other than the Attack or Cast a Spell action on your turn, you can use a bonus action to make one weapon attack.
6th level, - Instead of the feat, Fighters get either an additional Reaction or an additional Bonus Action (their choice) per round. At 14th level, again instead of the feat, Fighters get both.
8th level - Combat Readiness: you may use the lower of your levels in the Fighter class and your Proficiency Bonus instead of any other stat bonus when calculating initiative. Feats are cumulative with this. (Note that this solves the TWF problem.)
12th level - Sixth Sense: at 12th level your base passive Wisdom (Perception) scores become the better of 10 + Proficiency Bonus or 10 + Wisdom modifier and you may use your Proficiency Bonus instead of your Wisdom modifier when making active Wisdom (Perception) rolls.