Larian supporting Steam Workshop doesn't mean there will be any decent mods on there.
I mean, yeah... That would be up to the individual modders.
But Larian NOT supporting it would make pretty damn sure that there wouldn't be any mod at all.
Steam workshop gives you less mod control.
It is a nice easy button but honestly the BG3 mod manager is just download, drop in, drag over, and adjust the order if you need to.