In Rockstar North's defence, they are trying.
I live near their offices in Edinburgh, have friends that work on the GTA games, and encounter members of the development team quite often.
Honestly, straight-from-the-horses-mouth - they try. One time a R* North dev asked me what I'd improve about GTA, and I told him all this stuff about the flawed mission structure, the lack of dynamic structures (even if the world is dynamic), the mediocre gun combat, and he just said:
"We know."
He explained in very loose terms that they have been trying for years to improve all this stuff, but every time they try, it breaks, because the thing they're making is so massive that adjusting one thing in a big way impacts everything else. So, to prevent the games breaking, they keep iterating on how it was done in the past.
Which is fair enough. It'll just take a longer time for improvements to come.