> 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".

“I've come up with a set of rules that describe our reactions to technologies:

1. Anything that is in the world when you’re born is normal and ordinary and is just a natural part of the way the world works.

2. Anything that's invented between when you’re fifteen and thirty-five is new and exciting and revolutionary and you can probably get a career in it.

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