The problem is no matter what they would have done, people would find fault in it.
The 24 Aarakroca has a magical javelin that deals thunder damage and returns to its hand, but only the aarakroca can use this magical weapon and people complained it can't be looted and used by PCs.
The 24 hobgoblin uses a mundane longsword that can be looted but deals more damage when used by a hobgoblin to account for it's CR and people complain about that. You could say that they have special hobgoblin fey metal longswords, but the PCs would absolutely want to loot those for 2d10 damage.
So no matter which way you go with weapons, you lose. Magical weapon tied to the monster? No good. Mundane weapon scaled to appropriate damage per CR? No good. I guess give every monster claw and bite attacks? Or maybe give every creature over CR 1 three or more weapon attacks per round that do minor damage and hope you can win by attrition? (And drag each fight out to multiple round grinds)
Yeah, something has to give.