Operating systems from the biggest companies are rather stable and feature rich beneath for years now but that doesn't make these attractive in long term. Certainly not for the daily consumers. So they introduce all sorts of meaningless "featurettes" and UI/UX changes to pretend they work hard and thoughtfully on their products to create these never-ending "exciting experiences".

It's not about polishing to get it right nowadays but rather making a change for sake of changes because that looks good in terms of marketing.

As for this particular Apple case with all "26" versions and Liquid Glass: the backlash they got in June puts their actions along Microsoft's with Windows 8/8.1.