In 1912 (the last time we added more), the US population was ~90 million, and it's currently at around ~340 mil and we still have only 435 representatives.
1912: 1 rep per 20,000 people
2024: 1 rep per 780,000 people
This doesn't "solve" gerrymandering but it does blunt the effectiveness of it (among hopefully some other positive effects.)
The flaw is it doesn't mean anything so long as there's a 2-party system. Congress is stuck on part-line voting. Lobbyists only have to gain the favor of party leaders and the rest will follow. But one of the barriers to getting 3rd and 4th party candidates elected is there are too few seats that they can compete for.
Both solutions need to be implemented together. An expanded Congress is only useful with a plurality of ideologies. Getting alternative parties into office requires more competitive districts. Doing only one of those wouldn't be enough to significantly change the makeup of Congress.
This is indeed an interesting question, and I submit that the US is in an awkward state where the national assembly is simultaneously too large and too small.
I've seen some statistics that suggest that assemblies tend to start degrading in quality when you get past 300 or so: you end up in a situation where too many members just have nothing to do. At the same time, it's almost certainly the case that the US House has too few members for them to be sufficiently responsive to their constituents.