if you don’t think materialism is the best and effectively the only way to analyze society and come to conclusions and decisions on how and why to change it, why are you a socialist?

Because of foundational moral axioms regarding the ethical treatment of human beings. This notion of socialism as a purely materialist endeavor has always struck me as a bit silly, because materialism is non-normative. Someone could read a huge amount of materialist theory, ascribe to the conclusions intellectually, and still decide to be a rip-roaring exploitative capitalist.

And what other model would you say is as or more valid?

I think find instrumentalism/pragmatism comports with my framework better, but I don't begrudge anyone their choice of materialism.