Same for me. Medium, SubStack, and several other sites, have ruined any former good will and interest they once held. Instead of being sources for good writing they're 99% full of low-effort spam these days.
I still cross-post occasionally with a canonical link and haven’t seen any negative SEO impact, but Medium doesn’t drive nearly as much traffic as it used to. It’s mostly useful for tapping into specific Medium publications or communities—otherwise the effort rarely pays off.
Medium throws a lot of roadblocks up to your average viewership. Everyone I know (albeit mostly people in the tech industry) treats Medium URLs like Quora - avoid at all costs.