I still visit Cachy OS because I believe that it is good software but like you and others it’s an extra for me when I have time to experiment and try various distribution alternatives.
Regarding the immutable systems they won’t be my go to except when I have no time for installing and experimenting, then they have value as something that can be reliable (at least that is the intention).
For now my Debian alternatives are my every day drivers - antiX 23.2 is still the main one but I am helping with antiX 26 testing and soon that will become my base system. I also have MX Linux 25.1 and a few antiX respins to experiment with.