You bring up a good point I hadn't thought much about. If Luke gets offed soon (I pretty much expect that to happen), then we've got Rey, Finn, Kylo, and a smattering of secondary characters left to pick up all the dramatic weight. I'm not really sure how effective that can be. But maybe they'll recruit some more, good actors. Certainly, Oscar Isaac has strong acting chops, though I didn't get the impression that he would be a primary protagonist moving forward.There is something about Solo and Indy that was never meant to be a crotchety old man.
The servicing of our love of brands has made it a reality though, and it's not like it isn't interesting in some ways.
That being said, no crotchety HF - and relying more heavily on the highly questionable gravitas of Rey and Finn (without HF to play off of) - is going to be a massive test for TLJ... MH or no MH.
Hey, maybe that's where the Porgs come in.