Mids' Reborn only officially supports Windows 10 and 11 now. .NET is also up to version 7 as of a couple of months ago, 6 is now old. It just is what it is. Windows 7 is a 13.5 year-old unsupported operating system. There's just no legitimate reason for the Mids' developers to support it.
From what I understand, .NET 6 solved some problems that Mids' Reborn had. What, I have no idea. I'm not a developer.
Also, I recommend joining the Mids' Reborn Discord server if you have any problems or suggestions. For better or for worse, the two main Mids' Reborn developers (Metalios and Zed), don't pay much attention to forums. You can join it
here.