Medium is a business and it needs to make money. Donations might be a good stop-gap solution near term, but long term they need to figure out how to make money from other people’s writing.
What I think Medium does well is capture people’s attention and lets them discover new writers, new ideas, new perceptions and arguments. A writer can build a social media audience in a few months to a year depending on the subject matter.
Now the big question is would those followers pay money to read that writer or endure ads to read that writer?
I wouldn’t pay Medium if my feed was filled with articles such as, “10 ways to improve creativity.”
If I discovered a writer that I really liked though and that writer decided to write something a bit longer say a book that would be somewhat related to his/her Medium content. That. I would pay for that.