The problem isn't the actual shooting, it's how bad movement during combat still is, not to mention the dynamic crosshair (which should be permanent), and "tap to sprint" which shouldn't be a thing anymore. I never used auto aim, and it's still a clear step down from the best of shooters, of which Rockstar has one of the top contenders in terms of mechanics. Then you layer in the Euphoria weirdness, the laser accurate enemies, the health system that doesn't fit the game; it's just a bunch of things that make combat, at times, disappointing for me, especially missions dealing with tight spaces, or a lot of cover and enemies pouring in from different directions.
It being "just the right mix of GTAIV and MP3" means there's still GTAIV in the DNA, which means there's still "terrible" in the DNA. GTAIV should be gone. All traces of that game, from a mechanic standpoint, should've been nuked from orbit. They already learned how to fix all the issues.