It's a completely different game when it comes to production. They didn't copy and paste, they made a new game because the old one was outdated. If they weren't making a new game they would've just made a new DLC, this isn't a sequel. It's just a polished version of the first once because that's what it was meant to be. Still though, when you're using a new engine, new programming, etc.. you can't expect flaws because they haven't been using them the past 3 years. Maybe if you learned how difficult programming can be you'd know why they haven't made it perfect by now