Consider that for each representative you add, each individual representative becomes less influential and has fewer opportunities to affect change. While I do believe the house should be larger, perhaps 600 representatives, once the house gets too large you simply won’t be able to allocate speaking time on the floor in a reasonable way.

The house would organize itself around voting blocs and certain representatives would naturally end up exercising an undue amount of sway because they control those blocs. With each individual representative having much less influence, they’d have no choice but to gang together to try and achieve something.