Nomad dev here. I'd love to hear unbiased answers to your question, but here are my biased thoughts. :)
> Can anyone elaborate on what that immaturity consists of at the moment?
We're pre-1.0 for a reason. While you're right we leverage Consul for discovery and health checks and Vault for secrets, there are still quite a few gaps we plan to fill before hitting 1.0. We need a plugin infrastructure to support volume and network plugins. There's still resource constraints to be added (eg gpus) or improved upon (eg storage accounting). I'd personally love to get secure mTLS bootstrapping via Vault to be as painless as our server discovery via Consul. Lots to do, so expect regular improvements as we move toward 1.0.
tl;dr - The immaturity and pre-1.0 version are due to missing features, not instability or lots-of-breaking-changes.