We already have instances that go down or suffer from intermittent federation issues when lemmy.world gets a bit more active. The most conservative estimates are putting Reddit at 75 million DAU. If we get to 1% of that, you can bet that our current network would choke, badly.
Not only we need more instances, we also need to be a lot smarter about their organization and how to architect this network. I think we will only be able to grow larger if we make a more intentional separation between topic-based instances and "people-home" instances, so that we can have a better spread of the load.
There is less of everything. Less sports, less hobbies, less local groups, less crafts, less academic discussions, less indie hackers and entrepreneurs, less fashion/brand/style enthusiasts...
Memes and entertainment are too shallow and can be found anywhere, we need to focus on getting some people focused on the deeper end. Reddit's strength is in its long tail of interests. Instead of running blackouts or general protests, we should have focused on bringing one specific community to Lemmy (like e.g, knitting), figure out the issues and support them to migrate fully. If we pulled that off, other communities would have a template to emulate.