The first step is completely different from anything else you've ever done
"Pick an instance to sign up for"
This does not compute. What is an instance? Why do I have to pick? Which one should I pick? Compared to
"Create an account at reddit.com" makes sense and is something everyone has done before.
It doesn't matter how simple the answers to those questions are, the fact that the very first step requires multiple explanations is huge, and will always be a barrier to entry.
That's not how meta's going to do it; they'll start their own (with blackjack blah blah) that has better servers, better design, and other stuff real money can buy until theirs is the default. Then when they have the vast majority of users, they'll start throwing their weight around and others will be pressured to comply with the 'standard' they set.