The "an artist did it, the tools don't matter" point is true, but only to a point. An artist with a lifetime of experience using paint, colored pencils, and other traditional media A: is likely to not be able to reproduce that clean CG style and B: even if given the CG app that was used to make the examples above, would not necessarily be able to reproduce it, at least not without a whole lot of learning. At the same time, yes you could take a random person, train them to use e.g. Blender, and then show them that scene and they could reproduce it. It's arguably not even "art", it's more "illustration" or even "design", and there is lots of debate over the overlap of art, illustration, and design...
I am mainly interested to create illustrations, not art, and I am looking for the right tools and tutorials
there is no possibility of hiring an artist or any other specialist to do it, because of limited budget