This hasn't been true for a while. Unless you are constantly looking for only the most mainstream stuff, huge swathes of material is lost with every shutdown, especially now that the costs of servers and storage have quadrupled.

The idea of piracy being invincible is a myth from a different internet era along with old patterns like "platforms spring up and die constantly".

Yeah, in the 2000s that was true - but the main platforms we have today have been around for 20 years and have a stranglehold on users. The internet logic of the aughts no longer holds.