At the risk of being redundant:

Fix the algorithm

Get rid of the new bells and whistles and toys that were bought but never implemented

Find some way to reign in the number of "writers" (such as submit three samples of your writing, labor-intensive yes but it would improve quality)

Flush the site regularly to get rid of bots

Archive dead/inactive publications to make it easier for the rest of us to be found

Maybe a Medium for readers and a Medium for writers who are readers (hybrids). The former would be for anything except how to write on Medium

Fix the comment section scroll bar! I wanted to read all 160+ but anytime I commented on a comment I got kicked back to the top and had to start all over again. (I'm on a laptop if that makes a difference in whatever the bug might be.)

Put a limit on the number of publications that cover the same topic. Does Medium really need 25698725841587412 publications on "travel" for example? It makes it nearly impossible for newbs to decide where to publish. Plus a lot of the pubs end up closing because there are no writers submitting and no readers reading.

Prohibit site cheaters (follow-for-follow) from being able to monetize until they clean up the counts.

Create some type of tracking system for publication cheaters. The last time I checked a person was allowed seven (I think) publications. Someone on here figured out that if he had multiple accounts, then each account could max out the number of publications.

And that's just off the top of my head. I'm glad one of us is at the helm now. As a published writer and author I was assured by the last chief that all I had to do was write and Medium would do the rest.

I'm still waiting.