This idea of model-dependent realism [0] strikes me as a very mature approach to epistemology, which I was very glad to discover a few years ago.
As to what extent science is a human construct: personally I'm with you but I think many would disagree. I feel like Tegmark's ideas about the universe stand in contrast to the idea that science and maths is inherently anthropocentric.
For every scientist (or philosopher) worrying about an ultimate theory there are thousands more concentrating on solving specific and less universal problems.
There seems to be a popular narrative that suggests that because it might not be possible to come up with an ultimate theory, that science is fundamentally flawed, and that we should just give into mysticism or whatever “alternative” theory the author proposes.
This is a straw man argument. Science doesn’t have to solve everything.
By definition, it is a human construct: "the intellectual and practical activity encompassing the systematic study of the structure and behavior of the physical and natural world through observation and experiment"
Was this ever up for debate?
The real point being made is that the Universe might not be governed by finite, universal, consistent, "knowable" laws.
This is a point that has been advanced by several physicists. (My first memory was a book by Hawking.)
If it's not, science won't be able to know everything. But let's try anyway, because it's the best we can do.