It really is a trap, and it also doesn't provide the audience that it used to. It's annoying to users who aren't bought into their ecosystem (it shows popups trying to get you to log in when you just want to read blogs), it doesn't support syndication in any reasonable way (they have some broken RSS stuff that also includes comments, which is obviously wrong for blogs where the content should be prioritized) and any number of other problems. It's not syndicating to the widest number of readers, instead its locking you into their diminishing readership.
You really don't have to use Medium. It's trivial to get things indexed by Google if that's what you're worried about (generate a sitemap and submit it with their webmaster tools, everything is indexed shortly, or just write good content that gets linked from other places and those links will be followed), and you'll thank yourself later when Medium decides to arbitrarily kick you off, or goes out of business, or who knows what else that could cause you to lose access to your content because you don't own the domain.
You really don't have to use Medium. It's trivial to get things indexed by Google if that's what you're worried about (generate a sitemap and submit it with their webmaster tools, everything is indexed shortly, or just write good content that gets linked from other places and those links will be followed), and you'll thank yourself later when Medium decides to arbitrarily kick you off, or goes out of business, or who knows what else that could cause you to lose access to your content because you don't own the domain.