This is an even stranger opinion in a world where MGSV exists. Abysmal A.I., horrible stealth mechanics, glichy & distracting physics...yeah the gunplay felt weighty but it wasn't enough to make me enjoy playing Mafia 3. Which is a shame because when you weren't playing it, the game was fantastic.
I, and a lot of other people who played the game, wouldn't really consider mgsv an open world game. It's more of a sandbox in the original, pre-gta 3 sense of the word. Mgsv is like a bunch of Hitman levels strung together that you could theoretically walk through from end to end, but it's not really the point of the game.
And yeah the stealth is bad, but it's almost entirely forgotten the first time you get a shotgun. I don't think I ever used it once outside of the opening hour or so. It's just kinda limping there like a dead appendage of a system and if you want to dock for that it's fine, but considering the game is more than happy to let you forget about it and play with the superb gunplay for the entirety I'm more than happy to appease the developers there. I mean it's kind of like trashing the game's driving because they gave you the option to use that trashy arcade mode thing that makes the game feel like saints row. Just ignore it and have fun.
Also, to the other guy: I'm not sure what the mission structure has to do when we're discussing the core game play. I mean for sure the game is absolutely a fucking tepid slog that I couldn't in good faith recommend to anyone (seriously, anyone--if you're a story buff watch it on yt), but the core shooting and driving mechanics are really damn solid and definitely deserve a nod. Like, if you've played saints row then imagine the game forcing you to do every single block's side content and 80% of the take over junk before you could do a story mission. And unlike saints row, there's only about 3 different set ups for that content. Mafia 3 is a roughly 8-10 hour game that is stretched to the absolute breaking point of about 30 hours through nothing more than mind numbing tedium. Such a weird scenario for an aaa game, because normally it's the mechanics that falter over the structure. But I digress...