Sure! But, in this case Lemmy is literally a federated copypasta of Reddit, like Madtodon is of X.

This is being overly simplistic IMO. Lemmy is not a direct copy paste of reddit, just the idea is the same. Lemmy is missing many of the tools reddit has come to depend on for things like moderation and community engagement. The idea is the same but the framework is different and that comes with its own challenges.

Lemmy is a good enough platform for now and for future growth. It wasn't a drop in replacement for reddit when the exodus happened and it isn't a drop in replacement now, but it's closer. There are still lots of little things- quality of life improvements, moderation improvements, discovery improvements, etc that need to be tuned or fixed before Lemmy is ready to shoulder millions of active users, but that doesn't mean it isn't worthy of the effort today.

The beautiful part of the fediverse is we're all free to form our own ideas about how it's best grown and supported. If there's something you are passionate about there's nothing stopping you or anyone else from spinning up a community or instance about it and creating the niche communities everyone seems to miss. It all takes time, and individual and group efforts.