RDR2 is five years old this year if you can believe it.
I tend to think that if GTA Online hadn't been such a smashing success for Rockstar and brought in so much money we wouldn't wait so long between projects. I don't think it should be a regular schedule type of a thing where we get a new game from Red Dead, GTA, or Bully every other year like clockwork, and I'm good with waiting until a project is done before it gets released, but it is frustrating waiting for a decade and then some for a new game. At least with RDR1 and GTA4 we got side games that came out (Undead Nightmare and TLatD and BoGT respectively), but we didn't even get anything like that for GTA5 or RDR2 (and both RDR

and Bully are both dead projects at this point). I would have paid for DLC or a game set in the same territory that wasn't the main title, mostly because I don't play enough and consistently to make online worthwhile to me. It's just single player for me.
But because GTA

has been such a huge moneymaker for Rockstar I think they just don't feel the need to really push new projects forward. And, of course, given the environment we live in these days, Rockstar can no longer stuff their games full of tongue-in-cheek humor because we just know someone will be offended and that is a consideration (although they have been giving in since they took the Haitians out of VCS and replaced them with Mexicans because the Haitian community in Miami complained about stereotyping).
I am sure that there are people out there that can replace the Housers, but whether those people are working on GTA6 and whatever comes next is the question. Those are huge shoes to fill, but we won't see until the game is released sometime between now and the heat death of the universe whether they got the right people or not. But with Lazlo gone, the Housers gone, and several others who helped shape the tone of the games (and not just GTA but also Bully and the Red Dead series) it's going to be hard to do.