There's a few publications that don't even do that though and archive.is is very good at bypassing them so I do imagine they use logins for those, but for the masses of sites it's not currently necessary.
It just keeps getting banned from the addon catalogs because of complaints from media. The Firefox one was taken down by a french newspaper. So you have to sideload it, which is hard to do on Android.
Edit: it looks like even the github was taken down now: https://github.com/iamadamdev/bypass-paywalls-firefox
But yes it exists. And it works for most sites. It's just hard to get it now.