I have the same strong feelings about walled sites and tracking. May I recommend installing an extension to disable paywalls/tracking? Something like https://github.com/iamadamdev/bypass-paywalls-chrome (supports firefox despite the project name) which automatically wipes cookies from sites like Medium which enable "sign on" requirements after so many visits. It really improves the browsing experience.
I used to open these sites incognito or delete the cookies manually but it's really such an annoyance. Better to automate the policy of disallowing these folks to store cookies.
Then why visit such sites? I deliberately do not install extensions that hide problems for me. I want it to be cumbersome. I want to get annoyed so that I get discouraged to use the site in the first place, and I get reminded of that fact with every single visit.
If the few that do care still visits there is no incitement for the site to not do it.
Me neither. The forced login just reminds me that this is a site I don't want to visit, and a tab that I want to close. I'm not going to configure a workaround for every obstacle the site operators throw in my way; if they don't want me to visit, I won't visit.
I think they'll eventually learn not to do these things (see also cookie banners). But if they don't, it doesn't matter to me. There's other content available.
They need to make money. I guess they gave up on advertising directly and instead want to capture our info alongside what we read on the website to build profiles they can sell to marketers.