All the public ones are pretty bad. All the private ones with actual big players you can't access.
So unless you've got a close group of people who want to chat on TG, there is no point of trying to seek out quality discussion there. All of the channels are filled with pests that try to promote their scam ICOs, pump and dumps or TG HYIP bots.
Not the case with RUS-language public groups, surely you will find that most of them are trash, but a good amount of them is pretty good actually. But, you are right, unfortunately I never saw good/high quality private ENG-language TG groups, so cannot judge on that.
I think OP is looking for a place to discuss broader crypto topics, hence why he doesn't want DeFi recommendations.
Yes, you are very correct and this is what I was looking for. Not for DeFi/ICO/Airdrops/Trading Signals specific groups. If you have any good recommendations I would really appreciate if you would share some of them in DM.