They can improve an engine while it shows it's ancient age. The two are not mutually incompatible.
I put the bugs on bethesda and the engine. The combination is why it keeps happening, game after game.
I don't like this engine, but other developers use same engines for years.
It's fact. Problem with Bethesda is, they work on bought product, engine is not their engine. Ofc it's improved, but fact you can find bugs from oblivion in fallout 4 it's sign they are not really masterfull with engine. You don't need to update engine to fix bugs.
Engine yes its' kinda shit in form they use it, but games can be fun even with worse things.
Bethesda it's not AAA developer anymore, because of lack of talented stuff imho.
Rockstar use same enigne since GTA3, but they update it, fixing bugs, because (not 100% sure) it's their engine.
CDPR use same engine in W3 like in W2 and they use same engine for Cyberpunk 2077, but engine was made by them, so they are masterfull with tools and you could see effects. Same about Rockstar.
Also I think Bethesda will be sucessfull even with this engine, If they will start to fix bugs. Still remeber there's nothing like Bethesda's games, sure we have many very well crafted open worlds, but Bethesda's sandboxes are kinda special with all crafting, picking up objects, crafting and building. It's neat, but they really have to step up their game...hire more (just hire writers

) writers f, people who are good with engine and can fix bugs...
They are not monopolists anytime longer, and seriously Cybperpunk 2077 can kill TES6 and Starfield, RDR2 already mopped floor with F76 and W3 with F4.