i don't subscribe to the must have max stats to play your class idea, a Wizard with 12 intel can cast all the same spells as a Wizard with 16. a Fighter with 17 str does one more point of damage from hits as the same Fighter with 14 str and the Fighter with 14 str will also have at least 4 more points in some other stat like intel, dex or con which helps them in other ways... attack from high ground, turn invisable or just talk your way out of the fight are all worth as much as that single extra point of damage imo
just to be clear, play the game in any way you want so if having the max stats possible is your thing then go for it but its not the only option
I think you're underestimating the effectiveness of a single +1 ability mod in 5e, by not accounting for to-hit and by using absolute damage instead of relative. A fighter with 17 str also has a +1 to hit, which combines with that extra +1 damage for a decent power spike. Going from a +2 to a +3 Str bonus while wielding a d8 weapon results in a ~25% damage boost. That's pretty impactful.
While it's true that a fighter could otherwise put those points other stats for other uses, a fighter's specialty is combat. Similarly, a wizard's specialty is spells and arcana checks. Lowering primary ability scores will result in a more well-rounded character, sure, but somewhere you reach a point where you'll be so ineffective at combat due to frequent missing/enemies passing save that it might become frustrating and just not fun to play (assuming you're not playing in a roleplay-heavy game). Something something jack of all trades, master of none.
