When our forum transitioned from phpBB3 to Discourse, we lost many long-term users and community suffered… to the point where it crumbled and eventually shut down.
User feedback was basically the same as your friends. Actually what happened was that people were frustrated because they couldn’t find stuff anymore. They knew where things were in old forum but couldn’t figure out where to look in Discourse.
If I could go back, I would say that it’s not worth it 
… Discourse is great and I hope your community survives this 