Are you willing to put up with less security and a codebase with a single developer supporting it? I’m not.
Pale Moon is, very roughly, analogous to ESR Firefox releases, which are not as fully supported as mainline Firefox, due to stability and deltas in the codebase making it difficult to backport fixes.
It’s the red-headed stepchild of Firefox, in my personal opinion, and not something I’d recommend to people whom I wanted to be secure.
