I'm a bit of a scholarly infrastructure purist. The paper has a DOI, it leads to a landing page that has the full text, and the content is open licensed.

Like if someone posted a link to an archive.is version of a Wikipedia page, you'd probably prefer to get the canonical link to that content.

ResearchGate is a bit of commercial enclosure of infrastructure that is, and should be, open. Who knows, maybe it has other value. I'm not an academic so I don't know.