Maybe they don't want to risk a small game that won't make gangbusters because anything less will kill off this dying company. Even Starfield sold (barely) enough to offset the insane production cost (iirc), and that game was universally panned by all but the most midwit of midwits. No one talks about Blades, Legends (even after the shutdown), Castles, even a remaster of the mainline title Oblivion is largely dead not long after release when it came to discourse (I see more people talking about OG Oblivion despite less players, hell I saw someone playing a 3DS fan port).
They need big titles to draw people's attention, and if TES6 does even worse than Starfield they're shutting down. The TV show is just barely keeping the lights on, they're betting the farm on TES6 and I think they might just lose it.
They have the same problem most Western entertainment has chosen to adopt, in that they have bloated their companies to massive sizes, and thus can only survive off of massive blockbuster hits. Gone are the days of small scale projects that could make a modest but tidy profit, because you need to increase quarterly profits, and that means
more more MORE! There's no such thing as modest passion projects with small teams that you can use to train up new hires on a less critical project, or to let your creatives really go for it and see if they make a gem. Nope, there's just the 9 figure development cost juggernauts that need to pull a quarter billion or more just to
break even, and when you have that much money on the line, then every suit is going to meddle to try to make sure that the ROI isn't risked with silly little things like "creativity" and "appealing to the fanbase". After all, they need that mythical "modern audience" to make more money than before!
Personally, I think TES VI will sell because name recognition. Starfield didn't have brand recognition beyond "Bethesda" behind it to help bolster its appeal, but there are more than enough normalfags out there that loved Skyrim who will almost 100% buy We Wuz Septimz day one without an ounce of hesitation or skepticism. What will probably suffer is the game
after TES VI, much like how Halo 5 sold well despite a poor reception for Halo 4, but Halo Infinite did much more poorly since people figured out by then that 343 was fundamentally incapable of making good games. Usually it takes a massive turd or two in the franchise before fan loyalty really starts to wane, and I do not think that Elder Scrolls Online got enough notice from Skyrim fans to meaningfully reduce TES sales.