It's not complexity I have a problem with in fiction (I said to my friend in a conversation about same), but convolution. I don't hate it when a story has many threads or multiple layers; I hate it when they're there to serve no real purpose except to show off the author's ingenuity.
I don't need the author to demonstrate their ingenuity by making a story convoluted. I need them to do it by making the convoluted things of life coherent, by giving me a lens through which I can understand the messiness and damage of our world.
I've never been a fan of the idea that the only way to reflect the messiness and complexity of modern life is to have art that is also messy and complex. It's possible to have messy, complex art and have it be good, but to insist that the mess and complexity be prerequisites for saying anything useful or meaningful about our moment in time just seems like a cop-out. The most meaningful and useful examinations of a given moment in time seem to be by way of distillation and simplicity, or by way of metaphor, instead of through mimesis. Hence SF and fantasy: they tell us about ourselves by looking at what we hope for and dream about and fear, instead of just bouncing back at us something we already know.
One of the best ways to make a complex story simple is to find the unifying thread of the elements that introduce complexity, and look at the story along the lines of that thread. That way everything that's complex in the story is an aspect of that common thing, and it doesn't seem as overwhelming; it's variations on a theme, not cacophony. And again, I keep thinking SF&F are uniquely suited to that, because of the way they tend to hinge on a single big "what if?" to do their work. That "big what if" can be our lens, our way to reduce the complexity to a manageable metaphor.
(Something worth expanding in another post: We don't tell these stories because we're interested in their literal truth, but because of their metaphorical and symbolic truth — something we then translate back into real-world truth through everything we do after we've closed the book and gone on with our lives.)
At any rate, I don't feel like the job of a storyteller should be to make things complex, but to find the common threads in complex things that can be made into a clearer insight. And this seems especially important in SF&F, where the larger conceits of the story can work metaphorically and symbolically to help us reflect on our condition.