Let's say someone buys Planescape, Tashas, and Fizbans now.
What's going to make them buy those three books again in 2027 if the rules barely change
Especially since most of the updates are PC side. Crawford said the monster stats and CRs are staying the same. They are just adding the skills/saves/modifiers and redoing the layouts.
The new books would have to come out with new content. Such as being high level and in the broken stages of 5e. Or reveal new subclasses or races that WOTC already struggles with. Or create new classes that WOTC is hesitant to do. Or pump out new monsters with new tactical or narrative aspects.
and that's "bloat".
There is no way you are going to use the same rules skeleton for 20 or 30 or 40 years without bloat. New classes. New Subclasses. Now Monsters. New Traps. New Races. New Obstacles. New variants. New settings. Every year.
the "I'mma make corebooks, slow support to a crawl, and live off that" is one feasible for a small company with few employees that doesn't need much to keep going