Looks to me like a vendor specific language with limited capabilities compared to others. Just use Pulumi TypeScript (self hosted).
I'm not affiliated with Pulumi, it's just that unjustified vendor lock-in infuriates me.
We use it in our company to provision all our cloud resources. Granted, you can't create app registrations and such with it (yet) like you mentioned, and there are rough spots, but I think that is quite far from "not very useful".