Originally Posted by Maylander
At some point you need to start from scratch though. I'm currently (along with a big team obviously) in the process of building a business bank from scratch because it's simply not feasible anymore to keep working on the old legacy code. It's just not possible to upgrade it. Too many years have passed and the technology in use is too old. That goes for all legacy code. At some point it's basically a massive, outdated behemoth where every fix takes days instead of hours.
As for what's missing? Just play The Witcher 3. Fallout 4 was released about six months after The Witcher 3, yet it was years behind it in terms of technology. No amount of modding will fix the fractured world, the lacking facial animations or the broken physics.