Should I shave my head?

I really want to grow my hair out very long like I used to have it as a kid. Except back then it was straight and over the years it’s become wavy and very frizzy, and it looks horrible. So I’ve been straightening it for the past few years very often. I knew it would be bad, but now it’s gotten worse. It’s very dry, brittle, and full of split ends. My hair is also thin, and currently halfway down my back. As much as I don’t want to cut it all off, I don’t see anything else I can do to restore it. I’ve already tried different hair masks, treatments, shampoos/conditioners, and nothing worked. Would it be best to just shave it off at this point and start from scratch?