Zuranthium
Casting your favorite spell
Ability scores and ability modifiers are poor choices to display the difference between races in a TTRPG because the formula required to make it matter if too complex for in-person play.
Small differences matter. Stop saying it doesn't. No complex formula is needed whatsoever.
+2 racial modifier is already meaningful, because it means people pick those races to get the best stat they can in the area they care about most.
Until your total modifier is about 1/3 of the size of the dice you are rolling (for the d20 that's +7), The d20 overpowers whatever modifies you have.
d20 doesn't need to be rolled for everything. You keep insisting on these things as if that's how the game must be.
Difficulty checks should be based around rolling a D10, or an even smaller die, and no "critical fail / critical succeed" nonsense for most actions. No experienced swimmer is ever going to suddenly be terrible at it. Nobody who is bad at math is ever going to suddenly be able to figure out the answer to a calculus equation.
For some things there shouldn't be a roll at all. Just straight ability check: are you able to do something or not.
If you want a species to be strong or fast you need to write the rules that they are strong or fast.
Hence exactly the rules I said. It's not always supposed to be a huge gap though, like with Halfing / Ogre. For most races the differences are smaller, but those differences still matter and make things feel different. Halfling who is able to hit a higher sneak threshold than a Human can. Orc who is able to lift something up that a Human wouldn't have been able to. High Elf Wizard who meets the threshold to cast an extra spell per day than a Human because their +2 INT hits the breakpoint to do so.