The proponents of application registration are elitists who believe that the Fediverse should be run like the most toxic and exclusive club ever known to man, like, the kind you see in movies with bouncers who will assault you for walking past the place, not even trying to get inside.
They try and argue about network health, and continue to bring up the boogeyman of spam, but the reality is that they are elitist and want a specific user group on the Fediverse while keeping everyone else out, and they want everyone else to do it too. The fact of the matter is that what they are doing and encouraging is more harmful to this place than anything else, because without normies, this place is a ghost town.
Oh and spam can be dealt with without kicking out normies, I've outlined that systems which automatically ban spammers and purge their spam would work mostly the same as they do on the big tech platforms that almost without exception have open registrations. So stop using the spam boogeyman, it's an invented problem to justify your elitism and we see right through it.
It is bullshit and it will hurt Lemmy and the fediverse greatly in the long term since they've effectively crippled the onboarding process and turned their instance into a club.