I'm not convinced that this Rift thing is going to go anywhere. Especially not once Forge has been updated, at which point we'd basically have to update to 1.13 (well, the new Forge) again. It doesn't look like they'll be compatible and I'm not up for maintaining yet another (substantially different) version of the RM (1.7.10 has already diverged far enough, I don't need yet another whole mod loader to support).
Futhermore afaict the kind of networking which Rift seems to encourage its mods to use is fundamentally incompatible with the RM, resulting in it not working with any other mods.
And it's still using FG2 which, well, I've seen FG3 and I'd rather not go back.
It also requires one to inject tons of hooks into MC manually and instead of spending time on that (and every modder basically has to do it all over again) one might as well just use the same time to add the hooks to Forge once. That's also more or less the reason we use Forge rather than LiteLoader.
Overall I really don't see the niche which Rift tries to fit into, i.e. it doesn't seem to have any advantage over Forge or LiteLoader except that it's already updated (which leads me to suspect that it will die once Forge or LiteLoader are updated).