Many, actually. There are quite a few active alternatives now, such as Nebula for science YouTubers and Odyssey. Last I heard Linus Sebastian was working on an alternative as well.
It seems that most content creators are quite worried about the way YouTube handles (de-)monitization and copyright strikes. Many CCs are also streamers and use YT only as a side channel. Sure, YT still has a large footprint, but it's not as solid as it used to be.
There are, but generally for specific interests, and not nearly enough to challenge youtube's market domination. Without something dramatic youtube effectively has monopoly control of supply and demand.
It seems that most content creators are quite worried about the way YouTube handles (de-)monitization and copyright strikes. Many CCs are also streamers and use YT only as a side channel. Sure, YT still has a large footprint, but it's not as solid as it used to be.