Thanks for the feedback everyone, this has been very helpful!
After analyzing the responses here and in other places, we feel that the app menu and the window focus issue are perhaps less connected to each other than we previously thought, so we’re now thinking about addressing them separately.
Removing the menu has been largely uncontroversial – the majority of people liked the change or didn’t notice it. This is also consistent with what we’ve seen in previous user research exercises over the years.
The window focus animation, on the other hand, clearly needs more work given that issues like the blurry text being distracting/painful have come up quite a bit. It’s also possible that we’ve been overthinking this and the additional signifier is not really needed in practice, because most apps do have backdrop styling of some kind nowadays, as some people pointed out above.
The current plan is to land the app menu change independently of the animation for now, while continuing to iterate on better ways to indicate focus. We’re unfortunately quite constrained on what we can do (borders, shadows, etc. don’t work for technical reasons as noted above) but there are some new ideas we haven’t tried yet, also thanks to the responses and suggestions here and elsewhere.
Thank you all for your help, and keep an eye out for future experiments 