I wrote a reply and it vanished. From memory
Your first error is substitution. You are demanding that the contextualization that other people are claiming is the thing itself. Models exist because of the facts, facts don't exist because of the models. The idea that the scientific method depends on the assumption of materialism is a model, one that is not supported by the facts.
Humans, and really all known critters do not think first and then do. They do and then they think, sometimes. You knew how to eat long before you knew that you had to eat and long long before you learned why you have to eat. Effectively all the critters that have ever existed never once considered these two questions. We are rounding error.
The history of science is no different, just more extreme. We learned the basics of experimentation, repeatedability, measurement, peer-review whole centuries before anyone tried to put the process into context. Of course people like Kuhn and Popper failed completely but hey it's not like philosophy learns from it's mistakes.
You assume that materialism assumption is required to perform science is absurd as demanding that fish explain hydrodynamics before they are allowed to swim. The fish were swimming fine for billions of years before a human came around and modeled it.
Second, you are partially correct. Materialism is accepted because the data supports it. Not because it has to be prime ultimate truth. You are only partially correct because a. you do not advance a workable alternative and b. you mixup ultimate truth for tentative truth. What should humans do exactly? Not accept the best model for the data that we have until a better one comes around? And yes the belief in materialism is tentatively true. New evidence could disprove it. Which again, what would the alternative be? Everything is tentatively true, everything is subject to correction one day.
This is why Theology and Philosophy have always been stuck. It doesn't correct old mistakes and it demands an unreasonable burden to know anything.