First off Bethesda has this thing with using outdated engines so its very frustrating when their game comes out and has graphics that can't look good unless you mod them, also the engine and gameplay mechanics don't allow you to get into the game because your player feels to loose. Now I think the next game should build an engine similar to Anvil Engine, which is used for Assassins Creed games, now I only played AC3 and for the most part was not happy with the game, but the parkour and fighting was the most fun combat system I've played because it was so strict and tight on the controls I felt like I was in control of my character. In AC the ability to move character to character in combat with fluid action is great, and the ability to lay down traps and take out enemies easily one by one or even all at once was just so much more satisfying and the realistic damage was nice as well. Now here's how it would work (in my opinion) combat would be faster and more precise, also the ability to climb a tower to reach an archer and take his spot to view the area would be beneficial. Weapons would work much more different, all melee weapons felt the same but just slightly different animation, nothing felt unique, however if the combat was like AC each weapon type would have different styles and moves, also ranged weapons would work smoother allowing if wanted a auto-aim allowing to take out multiple enemies at once, sorta like an execution ability. So now that the combat is fixed now think about how cutscenes could be like, I like the dialogue but just standing there starting at a person makes it feel fake, if the characters moved around while you had dialogue it would really allow me to get into the scene.
Now graphics can always be improved however the engine Bethesda uses doesn't have a good gameplay feel, the normal hit and block gameplay is just to old and outdated to todays new combat systems, so a quick recap of how AC mechanics would be a success. You could roam the map quicker and more efficient by using parkour skills jumping from tree to tree, building to building, up walls and mountain sides. Combat would be more fluid, fighting would be quick and deadly allowing us to take on 5-50 enemies without taking a lot of damage by being able to counter hits and use people to block spells and arrows. Stealth would be smarter, being able to move cover to cover. Also A.I. would be smarter, archers would move away from the player instead of getting closer, brutes would attack in groups instead of one on one, and you wouldn't be able to walk in front of someone while crouched and still be hidden.
These are just key examples in my opinion to why the AC engine would work so much better, but I doubt Bethesda would pay money to use the engine so I think they should build a new engine that actually has good graphics and is similar to AC's.