I explained in another comment to someone else, but to recap Lemmy.world has lemmy’s registration applications feature turned on, but behind the scenes they run a bot to approve everyone who types the requested thing in the box. You sign up, type the thing in the box, and you get immediate access.
Compare this sign up process to the instance that the Lemmy devs run on Lemmy.ml.
Now to be clear, I’m not saying it’s unjustified. Trolls and spammers are a problem on Lemmy and we need more tools to help. Most instances require registration applications and I think that’s necessary for anyone without a team of admins across the world.
But that doesn’t change that it’s a big barrier to entry. Facebook has thousands of people able to respond to reports in a short period of time. Decentralised non-commercial Lemmy instances can never meet this, so we have a problem that needs a solution.