The control center toggles specifically tell you what’s happening (“disconnecting from X until tomorrow”).
If that isn’t what you want to happen, you go to the Settings app and turn off those toggles. (But I wish they would have a matching statement on screen that clarifies their changes are permanent until you change them again.)
Temporary toggles being in the control center is great. Most of the time that I quickly disconnect from WiFi or Bluetooth, it’s to solve some immediate, temporary issue.
The settings aren’t “changing themselves” — they’re doing what you asked them to do. The written message tells you what you asked them to do in order to teach new users what these buttons do.
So much for not changing settings by themselves :)