I used zsh for a few years before oh-my-zsh became a thing.
I have to admit that I don't find it more convenient.
It takes an ecosystem where things have a way of working, and establishes new conventions on top of those using a new set of environment variables. So if you know zsh, you don't know oh-my-zsh.
A vanilla zsh will feel very bare.
A vanilla oh-my-zsh will feel very feature rich.
If you end up configuring zsh anyways, I don't see the point at all.
Fascination in combination of interesting tools with very interesting tools in a very very unconventional workflow.
I like it.
I'm certain that I will not use the same workflow but it gave me ideas for my own.