Morrowind was not only my first ES game but also my first (modern) console game.
(My gaming before was on computers but upgtading video to run Morrowing cost more than an XBOX. And living room gaming is easier on the back than sitting for six hours+.)
My take is that MS shoudn't look at their IPs as individual games but as franchises and all recent evidence (Master Chief Collection, Tony HawK, Mass Effect Legendary, emphasis on backwards compatibility, the need to stuff Gamepass, the recent old COD revival, the prospect of updated transformers) is that there is big value in updating the old games. The older the game, the bigger the value.
Oblivion is playable today
Morrowind is barely so because of the animation, and aspect ratio. And the first two games need a full remake, not just a remaster, because they can't be payed on console or cloud. There's money to be made in remaking them for modern platforms.
And the fact that the remake can be farmed out in part or in whole is added incentive. Big games that can be had cheap.
Now, as to an Oblivion remaster vs Skyblivion there it the matter of (ahem) lucre.
A remaster can be sold as a new, standalone *commercial* game. Skyblivion? Hard to know. More, can Skyblivion even run on console or cloud?