What is elementary to you?
How long have you got? 😉
There are many aspects of reality that seem elementary to me, and at the same time, the totality of all the aspects is so complex that it seems likely that should I live the rest of eternity it will still appear mysterious to me.
And for me, it seems most likely that we got here as the result of a set of systems, rather than as the result of any intentional activity, and I can understand that it might not seem that way to many others.
I tend to view things in terms of systems, incentives, rate limiting steps, and flows of energy and matter. I use the tools of logic and mathematics to evaluate those things, and some systems are not linear – so are not predictable, except by trying them and seeing.
And the reality of the complexity of the number of interacting systems is such that none of them (even the linear ones) are ever entirely predictable. We can understand general trends, and there will always be subtleties that evade prediction.
Human beings are extremely complex entities, far beyond our ability to predict in detail, however good we get at predicting the averages, there will always be outliers.