It feels like we're approaching a situation where good clean astronomical data is going to have to be collected off-world.

Like, people in astronomy must be talking about such a scenario and how far away it is and what needs to be done.

A moon base seems like an obvious solution with dishes and telescopes all over the place.

Capitalism sure is efficient at exploiting externalities. SpaceX gets to ignore the difficulty and cost of stopping radiation pollution. The cost gets externalised to research institutions, academic researchers, government agencies (and so indirectly the taxpayer), and other corporations. Whereas it might cost $X for SpaceX to not cause the problem in the first place, it might cost $10X or $50X or more when everyone else has to duplicate cost and effort to overcome SpaceX's pollution.