Following on from my previous post of a few days ago about taming UI inconsistency in macOS Big Sur, I've now returned to the settings that I've used in the past, accessed through System Preferences > Accessibility > Display, turning off transparency and increasing contrast.
It's a pretty blunt tool, but it has the desired effect — the menu bar stays consistent. It also makes the overall UI much, much clearer.
Some might consider it ugly, or a throwback to the old days. To them, I would politely suggest that maybe modern UI designers need to reconsider whether they're 'fixing' things with their obsession for flat design and low contrast.
The early graphical user interfaces were partly constrained by the hardware of the time, but in many ways they succeeded in overcoming those constraints. And while it's great that we have accessibility features built-in to our devices, I think it's a mistake to consider those as 'only for people with disabilities'. In reality, our abilities can and do change during our lives, and modern UI design needs to start taking that into account.