It's my belief that much of this flavor of UI/UX degradation can be avoided by employing a simple but criminally underutilized idea in the software world (FOSS portion included), which is
feature freezing.
That is, either determine what the optimal set of features is from the outset, design around that, and freeze or organically reach the optimium and then freeze. After implementing the target feature set, nearly all engineering resources are dedicated to bug fixes and efficiency improvements. New features can be added only after passing through a rigorous gauntlet of reviews that determine if the value of the feature's addition is worth the inherent disruption and impact to stability and resource consumption, and if so, approaching its integration into the existing UI with a holistic approach (as opposed to the usual careless bolt-on approach).
Naturally, there are some types of software where requirements are too fast-moving for this to be practical, but I would hazard a guess that it would work for the overwhelming majority of use cases which have been solved problems for a decade or more and the required level of flux is in reality extremely low.