In fairness, I think a big part of that is the length of time the after market modders can take in order to make their code efficient. Game devs just don't have that kind of time and/or resources to spend on tweaking efficiencies.Skyrim is ancient, but with modding looks just as good as current games. But it runs in muuuuuccch slower/older hardware with ease. And stays smooth.
Makes you think, right?
This guy gets itRuns on older hardware because its an 18 year+ old engine .
IMO Skyrims engine is straight up garbage. Bugs that have been w/ the engine in Morrowind still exist. Its completely single threaded. Running above 60FPS and physics breaks. The engine can look great w/ mods, it sure don't run great tho.