I get that all the time. Some people are too rigid with team requirements on easier content, it’s annoying. Some tougher content may require a bit of selectiveness, but if I can solo it, then odds are I’d be fine on the team.
But I agree on solo runs. Most challenging thing I’ve done in the game thus far is doing TF’s solo. You learn a lot about game mechanics, and what works on your class and what needs improving.