I go on group rides all the time where riders can be and are dropped all the time. And that's fine for those rides: they're on the same route every week, they're known as race rides, that how hard they will be is dictated by the wind and who shows up, and everybody knows that they need to be self-sufficient and can get home on their own if necessary. But that's known up front.

It's quite a different thing when it's a small group, you were told it was going to be one pace and no-drop, and then when you get there it's now all of a sudden "HTFU we're not waiting for you." That sucks, and if it were me, I'd find other people to ride with.