I don't think such an aggregator is required. Interoperability is smooth enough that you don't have to think about different instances most of the time. I've only really noticed two points that would be confusing:

• the sign up process
• the "local"/"all" distinction

So I think what we really need to do to make this platform intuitive to people that aren't already familiar with it is:

• Somehow streamline signing up. The process from googling Lemmy to having an account on an instance should not be confusing or intimidating.
• Filter by "all" by default. The default should cater to the users which are less likely to figure it out themselves. If you don't understand what instances are and what "local" vs "all" means, then you are probably here for the "all" experience. If you understand and really want "local" you are probably fine having to set it yourself.

I have to image that most people with no intention of staying would not make accounts. Registered users are probably at least contemplating staying here for more than a couple of days. So the question for me is: will the communities here build a critical mass to sustain themselves after the blackout?

For me personally it's very simple. I will keep using Lemmy if there is enough activity to be worth it. I don't need it to be perfect or as active as Reddit or whatever. Just meaningful enough to warrant my time. I will keep my Reddit account for the time being, though.

I really don’t understand the benefit of being federated

The benefit is to prevent this from being the next Reddit. Being a nonprofit doesn't really guarantee anything in the long term. OpenAI was a non profit and now it isn't... Rather than trust a single entity to not abuse its power, federation aims to not give any entity all the power to begin with.

It also solves practical problems. Which single benign entity would pay for the servers and internet connections to become the new reddit? I don't think there is one.