That’s absolutely still true. I just disabled Spotify app link handling, and then Spotify opens in Firefox on my phone. And on Desktop it works the same way.

When I open a Spotify link as a webpage, I can't play that song unless I have an account. At some point in the past you didn't have to.

You always had to, in the past it gave a 30s preview. It still does that in Discord.

At least for me in the Netherlands, for the past month if I click a link to a specific song, I get redirected to a page to start a radio based on the artist and encouraged to upgrade to Premium.

I've had to get friends to share the titles manually, before I found Odesli to be able to convert them.

Right, but before it just loaded the page of the album/playlist and told you to sign in to your account. It has never allowed you to play songs without a sign in.