Let me explain the negative association:
* Popups and other pleas to make an account.
* Half hearted articles much of the time, linked to.
* Seeming a platform for self promoters with much noise but little original substance.
* That drags everything else down.
That said, I never did see it as much. I'm not much attracted to substack unless very specifically linked from another source, My association there's with people with many words that they want to shove down my inbox; people with many words that they want to shove down my inbox are also often more focused on 'readership' than sharing deeper stuff - deep is by definition harder to cognitively access than surface.
From sighting a URL I'm far more likely to go with a url I've never heard of than Medium/Substack/et al. While firstname_lastname.tld is very often a sign of quality, in my book giraffepoop.wtf is still > Medium/etc.
As for why others post there? Well, in theory it's free visibility, since there's the chance someone may find your work when viewing another article. And the paywall setup is easier to use than setting up your own monetisation system on your own website, especially if you're very non technical.
But all these things are becoming less important over time, and I suspect the majority of popular creators have just moved onto Substack or other solutions entirely.
This includes "ad-blocker blockers" and related nags and bitching.
Paywall bypassers that clear cookies help at times. Bypass Paywalls Clean left the extension stores and has to be manually installed.
https://gitlab.com/magnolia1234/bypass-paywalls-chrome-clean https://gitlab.com/magnolia1234/bypass-paywalls-firefox-clea...
Also opened 5 articles to see if there is "3 article per day limit" as usual, not happening.
Everything I post is set to non-monetized, so what you might see is just people ticked that monetize box.
Without login: https://imgur.com/a/ioFGzrM With login: shows a "Become Medium member for $5 per month" header link
Maybe it's different for regular users?