for example, the most highly evolved plants reproduce by means of seeds, and, in the most advanced of all plants (angiosperms), a reproductive organ called a flower is formed.
The existence of higher mammals and higher animals implies the existence of lower mammals and lower animals, and therefore possible devolutionary directions.
I suggest you read the wikipedia link? The terms higher and lower are, as far as I understand, mostly just there for classifying the amount of complexity present in an organism - there's not some "these organisms are better than these other ones" thing going on.
Unless you mean something entirely different than what most people mean when they say "devolution", what you are referring to is just evolution. The same way that "reverse racism" is just racism.
evolution can be both 'progressive' and 'regressive'. [...] if a population deteriorates genetically it certainly is something like 'devolution', and this article completely ignores this issue. [...] deterioration, misconceptions aside, is a real thing, and we need to stop giving people the impression that it is only a 'fallacy'.