1. XMPP is solid. But without XEP is very limited. Client based on pure XMPP is almost unusable for people.
2. Tried to get list of supported XEPs for gajim. https://gajim.org/support/extensions is dead link - bad way to persuade me.
After spending some time of googling, I have got list of supported XEPs. Will give it a chance again.