I use Opera for research with many tabs open, between dozens and hundreds (and occasionally upwards of two thousand). Opera is the one web browser that has historically supported my workflow well; Chrome and Firefox do not handle this many tabs gracefully. The old vertical tab cycler allowed easy and instant scroll-wheel navigation through open tabs in order of recent use, with dense display of dozens of them.
Even on a 1440p screen, the new horizontal tab cycler only shows seven tabs. I don't want a thumbnail preview of my tabs, I just want the titles. The old one was instant and allowed me to quickly find and switch to the tab I needed, and the new one takes appreciable fractions of a second to render on a powerful desktop computer, and even more if I need to scroll past the first seven tabs. It's glacially slow on my laptop. This turns an integral function of the web browser, which used to take less than a second to use, into a multi-second ordeal. It is making my work much less efficient, and I am able to get far less done.
I have been using Opera since Opera 8. The tab cycler behavior has remained roughly the same for a decade and a half. This stability and performance is what I have appreciated most about Opera: I had it set up the way I wanted to allow me to work in the most efficient way possible, and unlike Chrome, the developers hadn't (until now) made intrusive and degrading changes to core browser functionality.
I didn't ask for and do not use the "search in open tabs" feature, and even if I did, there's no reason for it to require me to change to a new, flashy, and objectively inferior tab cycler. This, again, is core functionality! It should not change without my consent, let alone be replaced with a shinier, slower, and more difficult-to-use version!
I have talked to multiple people on this forum who are having the same problems with it. We found and used the flags that let us revert to the old tab cycler... before they were removed, for (again) no obvious reason. If I was able to easily find and talk to users impacted by this change, there are certainly many more people upset with this. There's no official feedback mechanism to tell the developers I don't like the change. Your telemetry can't cover this.
I haven't seen a single post on here, whether it's my issues with the tab cycler or others' issues with the removed "recently closed tabs" menu, by someone who actually likes these changes.
Please, let us switch back. I want my browser to work well again. My only other option is to disable auto-updates and install a version before this change, which is obviously insecure, and I don't want that.