Eh, if lower contrast is an issue, make the background or glass tint darker, and the foreground content lighter, or viceversa. Good contrast is a challenge with any design element, regardless if it's using a solid color or this glass effect.

Things happening in the background being distracting and disorienting is also very subjective. You can lower the translucency of the glass just as you would lower the opacity of a solid color.

My point is that your criticism is far from being objectively true. There are ways of integrating this design element without running into those issues. The screenshot from the Forza game looks fine, for example, and having seen it in action, the background is not distracting. And what you gain is a more interesting and visually pleasing UI than if you were using a solid background. This may be more important in a video game, but it can also be done tastefully in OS and web design.

Forza is a game, the background being distracting or not isn't a real problem. On Windows 11 however there is some transparency effect here and there and it's indeed very annoying when a window change color because of what is behind it. Thankfully there's a setting to turn that down.