Many times it is just user error. Not cleaning the walls. Paint with teflon in it to stop to keep dirt sticking to it. People painting walls and not waiting long enough to cure before putting up decals. I see a lot of complaints on sellers using Wall decals, which is why I have never gotten into it. Too many reasons, to stop them from sticking. Maybe try the GreenStar indoor. From the color charts if appears to be General Formulations vinyl. I use the outdoor General Formulations without any problems.
I used some Oracal 651 on a wall here. It came right off, heating it up with a hair dryer before peeling it off.