Natural selection is not primarily about the creation of new complex forms, but about the preservation of already-existing complex form.
This is primary and necessary because of the spontaneous tendency for the degradation of complexity by spontaneously occurring damage: de-differentiation is natural.
Indeed natural selection is very poor at explaining the arising of novel forms. Very poor at explaining genuinely new adaptive forms.
Natural selection is good at explaining modification of already existing forms - by re-shaping mechanisms such as partial amplification or suppression, combination - but not good at explaining truly novel forms.
I would go further: there is not, and never has been, any observation or experimental or empirical evidence that natural selection can create genuinely new complex form - not from Darwin until now has there been any such evidence.
That natural selection alone can do this, can create new forms, can by itself and without aid from other processes lead to the whole diversity of life... is an assertion purely based on theoretical arguments. And the theory that natural selection can actually, in real life, make new forms is not convincing, since it takes for granted the pre-existence, the reality and identifiably, of forms.
The Red Queen mechanism of natural selection was originally formulated and elaborated as a special case, a phenomenon sometimes found, but usually not found. It is the idea, from Leigh Van Valen and named from Lewis Carroll's Alice Through the Looking Glass of natural selection working to keep things the same, rather than to change them.
Traditionally, Red Queen effects have been seen in phenomena such as 'evolutionary arms races', resistance to parasites and pathogens, and in the mutation selection balance (eliminating fitness-reducing mutations) regarded as a process which sometimes happens in particular cases... .
However, it turns-out that the Red Queen is universal, found everywhere; it is normal and usual; it is normative in the sense of being required - by maintaining already existing form, the Red Queen mechanism is what underpins and makes adaptation possible; what make novelty possible.
Because without the Red Queen mechanism to prevent the spontaneously-occurring loss of complex form, further adaptive complexity could not be sustained but would soon break-down.
So, this is what natural selection does - it does two main things: first it maintains (already existent) adaptive form; and secondly it adaptively modifies already-existing form. But it apparently does not create forms - rather natural selection works on already-existing forms