"People just like to complain"
This really isn't true. I have been using OneNote, avidly, for almost 15 years. Like many of us, I am an absolute evangelist for the product and continually bore people with how great it it. I literally could not run my life without it. In all that time, I have never complained once about any new feature or functionality, here, on any MS forum, or anywhere on Reddit.
However, this one change massively impacts my day to day (hour to hour) use and enjoyment of OneNote for the way that I work. It covers my writing and decreases the speed at which I can use the search functionality. I totally get that not everyone works in the same way, some people are on macs, some people are using different languages etc. And yes, it is not appropriate to be rude. However, it is appropriate to raise the fact that, for a significant portion of users, this change has been a negative step. It has made the OneNote worse for them, not better, and highlights that the search bar location should be optional and/or configurable.
This is legitimate feedback, not a baseless complaint, and there are clearly ways to make it work all users. I personally think it is great that MS are now being repsonsive to feedback and trying to improve the product in ways that work for their devoted user base - after years of neglect. Long may it continue!