Even if the degradation of the user interfaces is noticed especially by older people, I doubt that this has anything to do with them being old and I believe that it is caused only by them being more experienced, i.e. having seen more alternatives for user interfaces.

For several decades, I have used hundreds of different computers, from IBM mainframes, DEC minicomputers and early PCs with Intel 8080 or Motorola MC6800 until the latest computers with AMD Zen 5 or Intel Arrow Lake. I have used a variety of operating systems and user interfaces.

During the first decades, there has been a continuous and obvious improvement in user interfaces, so I never had any hesitation to switch to a new program with a completely different user interface for the same application, even every year or every few months, whenever such a change resulted in better results and productivity.

Nevertheless, an optimum seems to have been reached around 20 years ago, and since then more often than not I see only worse interfaces that make harder to do what was simpler previously, so there is no incentive for an "upgrade".

Therefore I indeed customize my GUIs in Linux to a mode that resembles much more older Windows or MacOS than their recent versions and which prioritizes instant responses and minimum distractions over the coolest look.

In the rare occasions when I find a program that does something in a better way than what I am using, I still switch immediately to it, no matter how different it may be in comparison with what I am familiar, so conservatism has nothing to do with preferring the older GUIs.

> Nevertheless, an optimum seems to have been reached around 20 years ago, and since then more often than not I see only worse interfaces that make harder

A consequence of having "UI designers" paid on salary instead of individual contract jobs that expire when the specific fix is complete. In order to preserve their continuing salary, the UI designers have to continue making changes for changes sake (so that the accounting dept. does not begin asking: "why are we paying salary for all these UI designers if they are not creating any output"). So combining reaching an optimum 20 years ago with the fact that the UI designers must make changes for the sake of change, results in the changes being sub-optimal.

> Nevertheless, an optimum seems to have been reached around 20 years ago, and since then more often than not I see only worse interfaces that make harder to do what was simpler previously, so there is no incentive for an "upgrade".

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3. Anything invented after you're thirty-five is against the natural order of things.”

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I believe it’s more about familiarity and being more resistant to change both good and bad