Plex has a weird centralization of accounts that frankly disgusts me. In combination of a closed source solution makes it even worse. I chose Emby instead. But both Emby and Plex (as well as nextcloud) are poor youtube alternatives in my eyes - at least for the scenario I'm thinking of.
Neither (correct me if I'm wrong) allows for comments for instance, and have a cumbersome interface for youtube-like watching and discovering.