I seem to recall that at the time The Force Awakens was released, people were saying that they would have liked to see the old gang together. But thinking of it, in the original trilogy, Luke, Han & Leia aren’t that much together.
But at least they WERE together in the OT. Now that the three films of the ST are finished, that doesn’t even happen once. I think that’s the point some fans are angry about. With the old films (and the old EU over the past years) they established a fundamental friendship between the main protagonists. Now it seems they were just on for an adventure 30 years ago, and that’s it.