For me, search integrated into the start menu was a major quality of life improvement. Particularly the ability to hit the Windows key and type the name of an application. Strictly speaking, this was introduced in Vista, but I feel like Windows 7 added a lot of useful polish to the Windows Vista style of UI.
I otherwise agree that the older Win 2k era UI was pretty much an ideal UI. The whole "frutiger aero" look did not age well.
I use the Win-key+[start typing] search all the time, but I also used it in the XP era. Only then it was a third-party app, with order of magnitude more customization and control. I actually have a worse experience now, but it's just above my tolerance threshold so I don't do anything about it.
Now you can hit the Windows key, type Visual Studio and open a Bing search for Visual Studio, instead of actually opening VS. It’s great - if your KPI is bing DAU
The Start Menu integrated search would have been real nice if it worked properly, but unfortunately they decided on some kind of “search” algorithm that can't even do a substring match on items in the Start Menu. I have no clue what the thinking there was, but it drives me to not want to use it.