I thought this, too, but someone did the math and were not as close to the boundary as you think. It's something like the Earth would have to be 10x bigger to prevent chemical rocketry from working.
From working at all, sure, but how big would those rockets have to be?
Rocketry doesn’t exist just because some idealists wanted to go to space. It exists because governments wanted to invent new ways to bomb their enemies. A V-2 allows you to bomb England from continental Europe (and wasn’t even a cost-effective solution for that); nobody was going to build a Saturn V-sized rocket for that use case, and even if they wanted to, it’s not clear that they could get it to work without lots of testing with smaller prototypes.[1] Compounding this issue is that, on this hypothetically larger planet, whatever enemies you’d want to bomb in the first place could also be much farther away! Whereas on Earth it’s not hard to reach any other point on the planet; a little over a decade from the V-2 we had ICBM’s.
[1] By way of analogy, Lofstrom loops are theoretically much more efficient than rockets, but to find out for sure we’d have to build a full scale example, and that would be extremely expensive even if we didn’t run into any unforeseen cost overruns or delays—which we inevitably would because this would be the first time we built anything like this. It would be like ITER except at least ITER has a practical application if it works.
