You may find your priorities as to what constitutes a good browser are not universal. Having a content blocker may be more important to many people than a tiny animation most people will barely notice. And... if you're not immediately used to a content blocker it's not a crazy idea to have something that actively draws a tiny bit of attention to the fact that something altered the page you saw, because content blockers do sometimes break pages, and thus users need to be able to find a way to disable it, certainly while the feature is still fairly new.
I think it's fair to say that you're never going to find a set of features and UI that have universal appeal, but if the UI really distracts you even after the first few times (I honestly don't notice it anymore), you could suggest a feature that allows disabling the icon or at least turning off the animation. Sounds like a reasonable request to me at least...
Just because people don't notice the animation doesn't mean they aren't affected by it. The smallest distractions can cause a loss in focus. A web browser is a tool I use for work, and it isn't just about what I want, it's about what I need.
I think it's fair to say that you're never going to find a set of features and UI that have universal appeal, but if the UI really distracts you even after the first few times (I honestly don't notice it anymore), you could suggest a feature that allows disabling the icon or at least turning off the animation. Sounds like a reasonable request to me at least...