Incomplete sets of monsters. This is my biggest problem with Rise. Jaggi/Jaggia but no Great Jaggi, Jagras with no Great Jagras, Zamite with no Zamtrios, and the worst, Crimson Glow with no Valstrax? Like why do this? It feels like not caring about the fans in a way. Completely unrelated to MH, but something I can compare it to as a wrestling fan is how WWE is the biggest it's been in years now because it trys to get new fans while AEW is getting smaller because it only caters to Hardcore wrestling fans and gives no backstory at all for a potential new viewer. That's how the Valstrax thing feels.
Another thing is that every time you talk to someone in the village you gotta skip some repeated dialogue. I love the world of MH and the fun characters dialogue is a key part of MH but I think they can still incorporate this without having to skip dialogue every time. That little time spent clicking A or X adds up.
A third is monsters that are designed only for multiplayer/impossible solo. I don't care how hard a monster is, the final boss should be super hard like Fatalis, but it still needs to be possible solo. It irked me so much that I could barely do anything about Kulve or Safi because I could rarely get the opportunity for multiplayer.
That's all I can think of now