Apple doesn’t allow content blockers on 32-bit devices “for performance reasons.” How is string matching slower on a 32-bit CPU? It’s the ads that result in worse performance! That’s not “performance reasons” – that’s “buy our new hardware” reasons.
Which isn’t too bad though… It’s a reasonable way to push new devices to customers – they get the latest version of iOS with security patches (and old features still working) – just not the new shiny features. Want new features? Get a new device.