As the type of guy who likes to ride the mass transit system in open world games, and just explore, I give that aspect of it a 10/10. I'll buy GTA6 for that reason alone.
As a game, it was what you'd expect. You go through the motions, enjoy the set pieces, get a dose of GTA depravity, and move on. To me, GTA is all about enjoying the atmosphere and the game world in spite of the middling gameplay. Even in the PS2 days, I found the on foot controls to be frustrating and unintuitive. Driving was mostly fine though. There were many, many games with better gameplay, but you stayed for the novelty of the open world, M-rated subject matter and extracurricular activities.
While GTA5's controls more or less improved over past iterations, I always got the sense that I'd get better gameplay from a dedicated third-person shooter. GTA's content isn't shocking anymore, so GTA6 is going to be 80% exploration for me. I'll still play through the missions though.