I think the success of expanded offshoots (OSRS, TurtleWow, Ascension, etc.) showed there is plenty of demand for games that add new features to older, slower, and more sociable games. many features in wow forever are lifted directly from some of these offshoots. blizzard leaning into things like sd models, no flying mounts shows this is beyond just nostalgia bait (something wow classic has been poked for) and indicates that these older iterations that had less streamlined experiences can still have a lot of juice if brought in new directions.