Second, it's been tried, multiple times. Saidit was one, I think. Ruqqus was another, and there have been more, all claiming to be censor free and all failing to achieve a solid following. Saidit was (and still appears to be) a cesspool of trolling, conspiracy theory and anti-everything-ism.
Third, it'll miss moderation, so it will probably follow in saidit's footsteps.
The trouble these alternatives have is their userbase have to be, in bulk, the users banned from the centralized social media apps. But if Apollo takes THEIR userbase, then those people arn't negatively selected. They're just people who have phones.
It's a better alternative to dying. Diversifying support for multiple backends could serve to protect you. Non trivial but it seems necessary at this point.
A RedReader/Apollo/etc. run alternative wouldn't exist for that reason so I think it would stand more of a chance.
I don't think Reddit will give them enough runway to have time to set that up though.
Possible related?
People don't actually want censorship free.
A direct centralized reddit clone without the god awful UI, dark patterns, and increasing poor leadership decisions would probably be an immediate success. Apollo for mobile plus old.reddit on the desktop would hit a million users in weeks.