Just champions wrestling period. Raw and Smackdown could use some non-title singles matches. The fact that they don't is one of the reasons why people say a lot of the recent title reigns are trash.
While I agree NXT does a better job at it, the main roster usually has more things to worry about than NXT. Like recently, having qualifying MITB matches and now KaQotR matches. Main roster isn't afforded the longer breaks between PLE/Specials like NXT is allowed.
It's not as bad as some think tho. World title just changed hands on Raw, Women's World title changed hands twice this year on Raw. SD has had Zelina on a bunch lately, before that it was Chelsea and the SD tag ladder match was an all time great. Dom always feels present on the shows. I'm sure there are other instances, those are just things off the top of my head.