I can‘t say that I like this rock solid write protection.
I think you misunderstand the purpose of the squashfs filesystem - LibreELEC is an "embedded" product and a read-only compressed image is the best and most convenient solution for distribution, and has nothing to do with "safety" although admittedly that is a secondary benefit.
Many config files can in fact be modified, but not all services support this so If you can explain what files you want to modify maybe more focused advice can be given.
Most of all I thought this SW was meant to be open to the community for fine tuning and experiments or did I get the wrong message?
There's nothing "closed" about LibreELEC, you just need to understand what it is and, perhaps more importantly, what it isn't.