The purpose of rules is to mechanically represent the fictional reality.
The purpose of the rules is to
be a game. Whether they are also sufficient for
other purposes is a matter of (furious) debate--and sure as hell not an objective "this
is the purpose of D&D rules." That's one-true-wayism if I've ever heard it.
We run into contradiction after contradiction if we demand that every rule must represent a physical part of the fictional reality.
Some abstraction is always necessary; the map is not the territory.
The difference is the same than with classes having bespoke spell lists and the situation where that is not the case and any class can choose any spell. In the latter situation the payer could still choose what was on the traditional spell list if they wanted, but it wouldn't be quite the same wouldn't it? Ultimately in a splat based game I want the splats to actually mechanically say something about the concepts they represent. if they don't, they serve no purpose. And every 'but this character is individual, so they can be different' equally applies to all racial traits and class features. What if this elf is unique and doesn't see in the dark? What if this wizard has studied healing magic? And literally everything else. If the desire is for every character to be an unique individual not bound by archetypes, (and that's a valid desire) then a splat based game simply is bad starting point. That sort of thing works way better in a game where the characters can actually be freely be built (usually with some sort of point system) by mixing and matching different things.
But spells are
creations; things
made by people, in-setting. It is completely expected that a plumber should know and understand different tools and techniques from those used by an electrician, even though both are involved in construction. (And the Bard--particularly Lore--has always existed in 5e, offering the opportunity to do exactly what you so pejoratively describe here as an intentional class feature.)
Further, the analogy fails because
in-character, ability scores are not elective; they are an innate part of the character. Spells are, and have always been, elective.
Some player choices should have a one-to-one mapping to character choices, but others needn't. Certainly, it would seem strange that the player choosing a race should map cleanly onto character choices, since (barring some rather strong sci-fi or magic elements), few characters
choose their race. Plus, y'know, the whole "ability scores significantly and permanently affect a character's overall success rate for the rest of its playtime" thing, whereas spells can always be replaced (whether completely, e.g. for Sorcerers, or simply by going out and learning other spells, e.g. for Wizards, or just picking different ones, e.g. for Clerics.)
And those other things seem perfectly fine to me...? There's a baseline for useful traits or physiological features, but even within the first year of 5e's life, we got SCAG offering things like variant half-elf options depending on one's ancestry. And with Tasha's, there's an easy way to represent characters who don't share some of the features of their normal race: the custom lineage. That's literally what it's for, to represent characters that
really REALLY don't fit the mold for their race. So...the "you're an X but you share few of their traits" thing would seem to have already arrived, without ruining everything forever.
(And for some reason some people seem to think that ASIs are the only form of ability generation. But of course they're just a small part of it. Most of your ability scores come form roll/point buy, so you still have a huge amount of individual variation.)
I find most of this "huge amount of individual variation" is mostly illusory. Every rogue is going to be at least moderately Dextrous--the incentives are too high, and the investment required to get similar benefits elsewhere is too great: they don't have Medium or Heavy armor proficiency, Sneak Attack requires the use of a weapon with the
finesse property anyway, and even Rogue subclasses that like other stats (e.g. Arcane Tricksters) still value Dex. Same goes for most other classes; every Wizard will have at least moderately high Int, every Cleric will have at least moderately high Wis, etc. Indeed, the fact that
pretty much all <Class X> want moderate-to-high <Stat Y> is what makes these ability score things an issue.
And yes, I can houserule anything. But everybody can. That's a total Oberoni fallacy.
If I were saying "the game is functional, you just have to house rule it," you would be correct. I am not. The game quite clearly functions whether or not races have ability score modifiers
at all. In fact, it functions literally identically either way, because the rules cannot even in principle distinguish between "naturally-rolled 18," "15 point-buy + 2 racial bonus + 1 from half-feat," and "14 from point-buy + 3 ASIs" (or even "14 point-buy + 2 racial bonus + 4 from Barbarian 20.") 20 is 20, whatever sum produced it.
What I
am saying is that, with other issues where you already know the rules are abstracted, you have demonstrated great comfort, perhaps even pride, in doing what you like anyway,
officialness be damned. If official sanction was not necessary before for other areas where the simulation model fails to conform to your expectations, why is it necessary
here, on
this issue?