One of the reasons why I find the new trilogy inferior (and also the prequels, to a slightly lesser extent) is that it introduces all kinds of new characters and then just forgets about them or kills them off.
It's only been three movies, but I'm guessing that the process of adding new characters was more marketing than storytelling. They wanted to appeal to a younger audience, and potentially set up additional movies to sell.
I think the way much of the events in TLJ were handled shows that they tried to almost forget that movie, and RoS is almost a direct sequel to TFA. I can't recall for certain, but I think there are only about 2 fairly major plot points from TLJ that have any impact on RoS, and that's Snoke's death and Luke's death. Other than that, I think you could watch TLJ and then RoS and not feel like you missed anything. That may be why some of the newer characters didn't last long.
