The knowledge about the material universe is there, it exists, but most people have a hard time accessing that knowledge, understanding that knowledge, and piecing it together in a way to see deeper truth.
I think there has to be an objective reality, whether we access it or not. It can't just be a bunch of brains each with their own created worlds inside of them, and nothing else. But I don't agree with you about some "experts" who access "the noumena" using a limited tool like science. Maybe some science-based guesses can be made and math would be the better tool for it than language, for the reason that language is metaphors (so humans cannot get outside of stories while using it).
The universe as "material" is a story. No one knows that the universe is "nothing but matter" or "nothing but consciousness", or whatever other story about what the fundamental nature of phenomena they want to tell.
I'm not looking out of my eyes at the screen just now. The screen is "here" in the same space as all my thoughts and memories and feelings... the whole universe, as known to me, is "here" in that same space. When I stick with the first-person POV then there's no "me in here" and a "world out there".
But when I start talking about "external reality", it bifurcates reality into two -- the phenomena alleged to be inside our skulls and the noumena that is alleged to be outside our skulls. So this fellow that
@pood mentioned, Wheeler, "agonized" because he thought he's inside his skull and then doubted any "outside".
IMO he should have doubted the dualism (in here/out there) better.
I mentioned metaphysical idealism in passing a few years back, and an engineer said "Idealism? That's solipsism!" I thought on that, and the more I did, the more clear it was that physicalism is solipsistic and idealism is not.
In the physicalist story, there are 8 billion different brains each doing their things wholly separate from each other (after all, what's the connection if mentality is confined to brains?).
In the metaphysical idealist story (and in cosmological panpsychism) there's one "brain", the universe, and we're events in it. So there's one consciousness and each little tidbit, that seems (but only just seems) like its own individual being, shares in it. So there isn't empty space between the activity of this brain and the activity of that brain...
However, if you feel more convinced of the physicalism story, science isn't your escape from the isolation it imposes. The reason is, as I was saying in my earlier post, science's consensus knowledge isn't agreement about the noumena but about the phenomena.
@pood's been making an important point. Science has a notable limitation -- it measures the behaviors of phenomena but cannot get to the fundamental nature of what the phenomena are.
This limit was a conscious choice back in Galileo's day. Spirit-matter dualism was the shared worldview at that time, and smart folk like Galileo knew spirit isn't measurable for being immaterial. So he and others decided that science's focus must be on matter, and spirit would be ignored by science - they left it in a different "magisteria". Then in the late 19th and early 20th centuries, folk decided, in effect, "let's just forget that whole other magisterium, the spirit or mind... all of reality is matter only!" Science cannot demonstrate that -- the maneuver is made in order to seem like they have a completed "true" story. But, again, science's "objectivity" is people inter-subjectively agreeing about what phenomena they experience. So if there's a noumena "out there" (which I doubt, since I lean towards believing idealism) then you don't get there from science.