I disagree. It's everyone's personal decision whether they want to pay or not. I was a non paying member for my first 6 months as I was trying to figure out Medium and see if it worked for me.
The free membership is Medium' s strategy for roping in new members and it does work as in my case.

There are many writers from countries where Stripe is not supported ,who DO have a membership but do not get paid for their stories.

Even if it's just $5 , it's that person's $5 and they get to decide if they want to spend it here or not.

Deciding to read a story or boycott it based on it's writer's membership status is discriminatory. Good stories deserve to be read irrespective of who writes it.