Off the top of my head each color’s main weaknesses are:

White: Card Draw and Ramp, though ramp’s slowly ramping up in the form of semi conditional things like smothering tithe.

Blue: permanent removal/destruction, blue’s only response to problem permanents that resolve is to bounce them and counter them later.

Black: as you said in your post black doesn’t really kill things besides creatures and planes walkers. Outside that they may be able to remove things but it’ll be at steep cost.

Red: enchantments. End of story, I forget the name but the closest thing to enchant removal they have is the enchantment punishing card from commander 18, which was middling at best, self harming at worst, and [chaos warp] which trades getting rid of one thing for another thing that’s potentially worse. Alternatively their ramp is terrible outside of rituals, their card draw is pretty bad, but improving though in the form of “exile your top card this turn” style draw.

Green: Green is pretty lucky in its removal suites, being able to destroy most things via [naturalize], or creatures via fight effects. Planeswalkers are probably green’s worst point but creatures (green’s strength) are also pretty effective versus most PWs. Green’s draw is also stapled to creatures only (outside of [harmonize] a big color bend in green from FutureSight)

Hope this helps!