What does offend me are all the bugs, as you say. It's still utterly broken all these months after the public release. Spotlight is a mess; I've seen it take DAYS before it has made an app in '/Applications' findable through search (even as the app shows up in Spotlight's long scrollable list of apps), and the animation where it comes in as a result of the four finger gesture has so many bugs I won't go through them all here. The most annoying is that it can end up in a state where Spotlight is not on screen, but you need to do the "make Spotlight go away" gesture before the "make Spotlight appear" gesture works again. It also often loads icons slowly; sometimes loading them in one by one over time, sometimes all at once after thinking for a second. It's arguably better from a UX design perspective than Launchpad was, but Launchpad was so much more polished and better performing.
There's also just constant minor graphical glitches. Things which pop in, things which load in with the wrong background color, that sort of stuff. The Settings app sometimes loads in stuff gradually and parts of the app jump around for a second before it settles, like a bad web app. It feels janky.
Mac OS X used to feel like a solid operating system. It has been going downhill for a while, but macOS 26 is the biggest leap in a long time.