The +2 ability score improvement matters when using the core rule, being 3from4d6. It also matters for other methods of ability score generation that make a natural 16 possible.
More importantly, it is the *flavor* that mechanics convey. Especially when the design discipline of bounded accuracy reduces the range of bonuses, small differences become rarer and more significant.
To pretend that a high elf with a +0 Charisma performance is an artist of poetry, music, and charm, is as eye-rolling as to pretend the half-orc with +0 Intelligence is the go-to race of wizards.
I think too many people get hooked on the idea that the scores represent something
real. 5E has arguably abstracted the value of scores
worse than any other edition because they are capped at 20 for
mechanical reasons. There's no
lore reason why someone couldn't be smarter than that. And some monsters have higher scores than 20, so obviously scores above 20 are possible, just not for
players. Which gives even
less meaning to tying the scores to a character's actual ability in anything.
Consider for a moment some of the greatest painters or musicians in history. These people were not
also naturally talented in Deception, Intimidation or Persuasion. Their +5 Cha applied
only to their ability to create music or art. We could argue that what this
really means is that their Cha score is actually +0, but that they have a crazy bonus to their "Perform" checks. Sure, we could say that... But that logic starts to fall apart when you start applying it to other things.
Consider instead someone who is incredibly well-learned in Botany. A person who could identify the genus of every plant they see, or quickly figure it out if they'd never seen it before. Are we going to say this person
doesn't have a high intelligence?
D&D has set itsself up for a problem by saying that "0" is
average but then turns around and says that "average" people make up the vast majority of the world. The cobblers, the farmers, the sailors, the carpenters. This means the "average person" is capable of telling the weather, judging the seasons, watching the tide, milling, tilling and chilling. Your crops are farmed by people who are neither particularly good or bad at anything at all, your cakes are baked by people who apparently aren't good but aren't bad at anything!
So, bringing this back around, it's absolutely silly to say that an elf can't be a great artist or poet because they have a +0 Cha, because the +0 is absolutely irrelevant to anything outside of the player's stat sheet, since the game has already said that
most of the people in the entire world have +0's across the board.