Let's take an example.
A new third party software for video games is available to generate "real", infinite and adaptative dialogues to all NPCs in function of your answers/questions and which would work whatever the hardware, even on toasters^^ (I believe it already exist, someone posted a video somewhere on the forum). It would be awesome for games like Bethesda ones. Unfortunately, it wouldn't be something that modders could access, modifying or whatever (impossible to share it freely or the tools would be overcomplicated/way too expensive to devellop). So in short, no new quest could be added by modders in games which use this "great" software.
For studios who don't care about modding, it's not a problem at all... But I'm pretty sure, in Bethesda case, they simply wouldn't use it, because the modding comunity could be quite angry, if it's impossible to add new quests (I suppose^^).
So in short, studios have slightly different priorities (which is understandable). I think (but I can be wrong), for Bethesda making moddable features (and provide good tools) is at the top, or almost, of their list. At least, more important than making awesome graphics (or writting a good story, but that, it's subjective^^).
So I will buy Starfield for sure, not for outstanding graphics, not for outstanding story/characters. But for a real good sandboxy RPG like always and hope for a full mod support on Xbox. Because I'll count on the great Bethesda modding comunity to provide an "Unofficial Starfield patch" which will fix all the bugs that Bethesda will never bother to fix (so yeah, in this case, it will be "Thanks modders")