YouTube has competitors, but none of them are very serious about the job. They're just kind of vibing in slightly-adjacent niches, afraid to take a bite at the top dog.
Depends on what your goal is. If you're trying to make a competitor to YouTube's original idea, bandwidth and storage are likely distant concerns, and copyright isn't a hard problem (because you can just accept DMCA requests like the rest of the world, you don't need to replicate contentID).
If you want Despacito and the Baby Shark Dance to be your top videos, it gets a lot harder.
Bandwidth isn't cheap, storage is a bucket load and than moderation & copyright. Let alone any other issues.