Micro-evolution is widely accepted, even among creationists. That is a "mechanism of evolutionary change."
It does explain.
The problem scientists create for themselves is they wish to see no purpose or plan in nature beyond random occurrence. The scientists reject God, therefore they reject anything that sounds like planned movement in nature. It all just has to be happening because atoms randomly bounced into one another.
I don't think you have to reject God to accept that the natural world operates according to very simple laws, and that this means "random" situations will befall different members of a species.
But we see that nature, at least here on Earth, has evolved in a direction toward greater complexity and awareness.
This is not true. Some species have evolved towards greater complexity and intelligence (awareness). But other species have not. Some species merely evolve to become more adept at handling their environment. For new species of bacteria, they aren't any more or less intelligent than the species they evolved from. They aren't evolving greater intelligence. So only a small fraction of evolution involves species becoming more intelligent.
And the fact that intelligence has evolved is not contrary to evolutionary theory in any way.
If evolution is merely leading to greater survival of the fittest, it could have stopped with sharks or with a shark that can defend against the few natural enemies a shark posseses. Instead, relatively fragile human beings are sitting around debating on the Internet - and still being eaten by sharks.
Fragile??? Man is the ultimate predator, at least as far as the Earth has seen (Predators are the ultimate predator, but they only exist in comic books and movies and video games). Man is an awesome predator. We've killed a member of pretty much every species on Earth (certainly almost every land animal; there may be some ocean species that have escaped our violence by living deep enough under the Earth). Individually, man might be weak compared to lions, tigers, and bears, but that doesn't matter to evolutionists. If we work as a group, then that's how we should be measured (biologists measure how things function in the real world, not how things would function in artificial settings). And if, as a group, we kill anything we want to kill, then we're the ultimate.
Survival of the fittest is itself a concept unique to living things. Living things are astoundingly unique as compared to inanimate nature. Why? Scientists don't know, and once again I will tell you they have observed natural selection and evolution, they have never identified its mechanism. Because they don't want it to have a purposeful mechanism. They want the same random mutations that fill jars at a freak show to randomly explain evolution. They don't.
In all areas science runs into a brick wall when it gets down to first causes and ultimate reasons for everything. The universe itself and subatomic quantum behavior get down to a point beyond which science says we can't see. So it doesn't matter what's inside a black hole, what existed prior to the big bang, or where a subatomic particle really is. But it does matter, and for some reason we care. And science has not found why.