You need some sort of verification that the person is a person. Phone number puts a layer between you and the service you are trying to use - the provider of the number. The provider holds your identity but only passes on a phone number.
It’s definitely not ideal, but not bad
I switched recently from Plex to jellyfin because Plex implemented stuff I do not need nor want, and it was full of bugs. Jellyfin works way better for me then Plex did.