So, I kind of infer from what you've said elsewhere that you don't equally endorse all possible evolutions equally. That is, when you say "evolution continues" you mean something rather more specific than that... continuing in a particular direction, leading to greater and greater amounts of whatever-it-is-that-evolution-currently-optimizes-for (this "complexity measure" cited above), rather than greater and greater amounts of anything else.

I don't understand your distinction between "all possible evolutions" and "whatever-it-is-that-evolution-currently-optimizes-for". There are possible courses of evolution that I don't think I would like, such as universes in which intelligence were eliminated. When thinking about how to optimize the future, I think of probability distributions.

And I kind of infer that the reason you prefer that is because it has historically done better at producing results you endorse than any human-engineered process has or could reasonably be expected to have, and you see no reason to expect that state to change; therefore you expect that for the foreseeable future the process of evolution will continue to produce results that you endorse, or at least that you would endorse, or at the very least that you ought to endorse.

Yes! Though I would say, "it has historically done better at producing results I endorse, starting from point X, than any process engineered by organisms existing at point X could reasonably be expected to have."

Are you actually saying that simpler systems don't ever evolve from more complex ones?

No. It happens all the time. The simplest systems, viruses and mycoplasmas, can exist only when embedded in more complex systems - although maybe they don't count as systems for that reason. OTOH, there must have been life forms even simpler at one time, and we see no evidence of them now. For some reason the lower bound on possible life complexity has increased over time - possibly just once, a long time ago.

Or merely that when that happens, the evolutionary process that led to it isn't the kind of evolutionary process you're endorsing here? Or something else?

Two "something else" options are (A) merely widening the distribution, without increasing average complexity, would be more interesting to me, and (B) simple organisms appear to be necessary parts of a complex ecosystem, perhaps like simple components are necessary parts of a complex machine.