The idea that all particles should "participate in physics necessary for the observable universe functioning" is not a rational position, unless you assume a premise such as "the universe was created for a purpose."
Without such a premise, it is completely expected that not every aspect of the universe should have something to do with its functioning.
Even in pure mathematics, with no dependence on the physical universe, you have
Gödelian unprovable propositions which, as Gregory Chaitin put it, are "true for no reason, they're true by accident." If the universe did not include a physical equivalent to this, it would be quite a surprise which would tell us that something very unusual was up.
I kind of see what you're getting at, but don't think you've described it well.
My attempt to restate your position: Suppose you write a program that just so happens to log information every leap day. No one uses the information, it doesn't effect the rest of the observable output. If you delete this logging from the program, no one else notices.
The complete observable properties of the universe (the program) include this logging, but the functioning of it is not really dependent on the logging. Thus, we probably should expect that there are some aspects of the universe that are independent, they don't really matter (or at least don't substantially matter) beyond their own observation.
The logging analogy doesn't capture what I was referring to.
Logging is a feature that someone deliberately adds to an application. It has a purpose even if no-one uses it.
I'm talking about features that (a) were not intentionally designed and (b) have no "purpose" - i.e. do not "participate in physics necessary for the observable universe functioning," per the original commenter.
The point is that for a feature to have a purpose implies an intentional design. If you assume the universe was intentionally designed, then yes, one might expect all features of the universe to have a purpose. Although as Gödel pointed out, this may not be possible - even intentionally constructed systems end up with features that weren't part of the intention, but rather are unavoidable consequences of the design.
If you don't assume intentional design, then there's no reason to expect that all features of the universe have a purpose.
The point is that in empirical science, we take our observations of the universe as the starting point. And not any ideas or theories of how we think the universe should function. There was a time before empirical science took off, that the latter was still the modus operandi, a lot of beautiful theories were made but in the end science got hopelessly stuck.
It's funny that we're a bit in a similar situation now. Again we have a bunch of theories, e.g. in cosmology and quantum theory, that are based on not much more than an idea of how things should be. The Great Unification Theory springs to mind for instance. And again we seem to be stuck.
I sometimes wonder if the laws governing the universe are a bit like a Taylor series. An infinite set of terms each with a smaller effect on reality quickly approaching zero.
Are you thinking of Einstein's comment about god not playing dice? Because that's perfectly consistent with what I was saying: he was implicitly assuming a kind of "designed" universe, in which case of course we have a stronger reason to expect that all features of the universe have some purpose.
(Although this is still subject to Gödel's caveat, that even intentionally constructed systems end up with features that weren't part of the intention, but rather are unavoidable consequences of the design.)
But if you don't make that religious assumption, then the expectation that all features should have a purpose becomes unsupportable. There's simply no reason to expect that, and even the notion of features having a "purpose" is misleading metaphorical language at best.
Back to the subject of what Einstein would say, we should also keep in mind what he wrote in a private letter in 1954:
> “The word God is for me nothing but the expression of and product of human weaknesses, the Bible a collection of venerable but still rather primitive legends. No interpretation, no matter how subtle, can (for me) change anything about this.”
I'm not aware of Einstein having written anything attempting to reconcile this with his previously expressed pantheistic views and the related views implied by the "play dice" comment. That would be tough to reconcile.
Another relevant issue here is that Einstein's dice comment was objecting to non-determinism in quantum physics. But in the nearly 70 years since his death, everything that has been discovered still points to inherent non-determinism. There are some theories/interpretations that would eliminate this, like superdeterminism and De Broglie–Bohm theory. But even if such a theory satisfies Einstein's concern, it doesn't affect what I wrote - such theories don't address the justification for features of the universe, they simply model what we observe.
tl;dr: what I originally wrote is essentially a tautology that neither you nor Einstein can refute.
Without such a premise, it is completely expected that not every aspect of the universe should have something to do with its functioning.
Even in pure mathematics, with no dependence on the physical universe, you have Gödelian unprovable propositions which, as Gregory Chaitin put it, are "true for no reason, they're true by accident." If the universe did not include a physical equivalent to this, it would be quite a surprise which would tell us that something very unusual was up.