Your estimate of followers to engagers seems about right for me too. I know lots of those who follow me will never read anything of mine. I've long suspected many of the random followers are newbies, following here like they would on Instagram or X. But, I'm sure some of them are people with multiple accounts who follow you with all of them to get you to follow back at least one.
You can usually tell those followers because all at once you'll get three or more with very similar profile looks and titles. Often, one or more of those profiles will clap on several of your posts in about a minute — clap jumpers. And, Medium seems incapable or unwilling to do the one thing that would solve the clap-jumper issue: freeze the claps until the reader has been on the page for 30 seconds.
Instead, the made the claps icon filled in so that it looks like it's already been read. What a mess.