So, here's a neat-looking thing: the Mafia II Final Cut mod
https://www.nexusmods.com/mafia2/mods/416

It's a mod for Mafia II, obviously, and it corrects one of the worst
things about the game. "Mafia II" was a great game, but its largely
mission-based structure was forced into a giant open-world map.
Although "forced" is somewhat disingenuous. The missions were tossed
onto the map haphazardly, forcing you to drive long distances to
trigger each one, while the giant open-world map got very little use.
It's a game that could have been a series of much smaller maps -one
per mission- and not been dramatically affected by the change. The
open world was sorely underutilized, and felt barren and lifeless
because of it.

Final Cut changes that by adding a lot of new features (cabs, buses,
trains, businesses to visit) and modifying the missions and combat to
make them more exciting and integrated into the world. It changes
"Mafia II" so that it feels less like that open-world is just
something you need to traverse to get to the next story-beat, and more
like a place you actually live in.

Final Cut has actually been in development for some years; a new
version (1.3) is scheduled for imminent release. If you're waiting for
GTA6 (or just haven't played Mafia 2 in a while) maybe pick up this
mod and give it a try. "Mafia 2" was a good -if flawed- game; this mod
aims to fix its worst flaw and maybe push the game to greatness.