I'm playing Starfield on gamepass. Fallout 4 was similarly a wakeup call for me: I had pre-ordered it and was mostly disappointed by it. I occasionally try replaying it, but that disappointment sticks with me to this day. This is coming from someone whose first major gaming experience on PC was with Oblivion (which I still play to-date).
So yeah - I'm with you on not buying Starfield new because of FO4's poor showing. I am enjoying it well enough that I may buy it someday (kinda wish I had gotten a GPU bundle including it just because I've been ready to upgrade for a long time), but I'm not in any rush to do so. I just knew I wasn't going to be as interested in it as I was with other Bethesda games of the past.
As an aside, I hope FO3 works better for you these days. A year or two back, Bethesda patched the Steam version to remove the Games for Windows Live requirement, which had foiled many attempted replays of mine (particularly when I made the move to Linux). Now it runs perfectly well.
If you have a source on this, please share it - I have not found anything to corroborate that he is being replaced by AI, although the idea that this is happening is plausible and believable.