I got around it by requesting desktop version. Markup on Medium clearly fails for mobile Firefox.

I use the Firefox extension "Hide fixed elements", which is not only useful for hiding these kinds of modals but also overlarge headers and cookie warnings.

That usually works but in this case, it’s not just a modal. It doesn’t show the article unless I sign up. No way to dismiss it either. It’s different than the modals I used to get last week.

I don't think there's any way around that pop up on a mobile browser.

You probably can block Javascript using uBlock Origin (for convenience) on supported mobile browsers.

Safari reader mode?

I forgot about that, Chrome has that too. That should work.

search for the extension "make medium readable again". I've come to see medium and google captcha as mental filters for judging the overall technical competence of the firm deploying them.

Any article there does not deserve to be read. You are not missing anything

That's not fair. Medium's content is community contributed. There's a lot of value in there. Let's not throw the baby with the water.

That community of content creators chose the platform for the benefits of discovery, SEO and convenience. While I agree that there's great content on Medium, those upsides come with a few downsites for content consumers and losing a few of them comes with the territory. It's still a net positive for creators anyway, otherwise Medium wouldn't be a thing.

if the author cares so little about their readers that they choose to distribute their content on medium, there's a good chance that content isn't worth reading.

An author may care so much about readership that they value reaching 50 million people, over a few dozens, if the price to pay is some inconvenience with the medium (see what I did there?)

What's so bad about it?

One easy way to communicate to said community that Medium provides a terrible experience for readers is by reducing page visits so that they start wondering about it and look for alternatives.