Safety Net is passing by default. If it's not for you, then you are doing something wrong or you don't have stock boot/vendor or you are playing with your device fingerprint or any other reason that Google doesn't like. Debugging it is really not a walk in the park...
It's funny because you are blamming devs for an issue that only you have... If a simple file explorer doesn't work, then for sure your installation is not clean as you say. Or you just don't know how to use android at all...I Liked a program called solid explorer but it doesnt work. Doesnt want to use folder , neither SD folder. I got a feeling adb tools wont work either.
The developers have quite got there balls mixed up with permissions . Doesnt make life easier.