The old "we don't want competitors to undercut us" thing is such a bad justification for switching to non Open Source licenses (e.g. Elastic, Hashicorp…). You can absolutely keep some features in proprietary extensions and make them available to enterprise clients while keeping the main software OSS.
Cluster mode, SSO, SCIM, audit logs, account impersonation, integrations with proprietary software, the list goes on and on. And these features are usually hard to replicate, good for you.