I don't care that it works for you. I have been using this software for 12 years, so I know how to use it. Stop making it seem like it's on my end when it clearly is not. Other people have confirmed it in this thread. It is broken! plain and simple! Literally, 3 people just said they have this problem. learn how to read before you assume someone else is incompetent.
Maybe you should make sure you're on the newest Start11 update and the newest Windows update
End of FRiNGE07's quote
Firstly lets all be nice to each other.
Secondly, I am unsure if there is some misunderstanding here.
The Mica effect has always shown you a blurred, darkened or lightened (depending on mode) and largely featureless version of the desktop wallpaper. The transparency slider does impact things, on Win 7 style it will reduce how solid the menu is over the effect and on the other styles it will where the background is not already almost entirely invisible (so top bar, or right bar area typically).
The Mica effect itself has light / darkness applied to it but generally is much less obvious in dark mode than light mode and it looks like your taskbar / startmenu at least is in dark mode.
If you look closely at your screenshots you can see it isn't a single tone, there is visible blue gradient showing which stops at the right hand side where it is darker. If you set the slider to 11% you will find the right hand side then matches the left showing it is doing something. What you are seeing is 100% mica with nothing painted over it on the left. I am guessing you are using the Windows wallpaper thats dark around the edges and blue in the middle.
I have tested v2.5 as well just to confirm there is no change here. As this is our own implementation of Mica it is also not being impacted by any OS changes which might have happened.
There were three different users posting here, one is banned for reasons I am unsure of, one is yourself and the other report is from someone who is reporting OS wide issues with transparency which would be an entirely different issue.
In short, as best I can tell the Mica feature in Start11 is both working as designed and working as it was before so I am scratching my head here as to what could be the issue. Please note that the effect is very wallpaper dependent and doesn't always show as well in dark mode as light. As a test set Windows to light mode and see if you can see the effect then.