I think a single person, if is not a master, has not enough power to change the world/reality.
I don't think that's how masters do it, either. Technically it's always co-creation from my point of view, though I typically don't use the term. But to me "reality creation" is the conscious participation in a process that happens anyway to all human beings, though most of them unconsciously. Though I also get the sense you might use the term "creation" to mean something like a miraculous act, maybe?

Affirmations alone have their impact purely depend on the strength of a person's will. While there can be value in developing such will, it's not easy and probably a hard way to obtain any result. Similarly people talk about the Law of Attraction from incomplete data.

Just in general, it seems to me we have made similar observations of reality. Different outcomes and conclusions surely, but I can relate to your basic data.