Mastodon seems like a better comparison. It has more than a dozen forks and clones, and plenty of donation income.
Sure it would be good to have more contributions in Lemmy, but as these projects are made by volunteers they will do what they are most interested in. Nothing we can do to change that. And if they add new features which prove useful, they can also be added to Lemmy.
New users for Piefed and Sublinks are most likely to come out of the millions of Reddit users, not out of a few thousand Lemmy users. So this will increase the size of the Lemmy network and lead to more activity.
Having other projects which are similar to Lemmy is a great sign. It means users have more choices available and developers can experiment with different solutions. It’s really not a competition, because the existence of more compatible Fediverse projects will also benefit Lemmy, as there will be more users and more content.
Sure the plugin hooks still need to be implemented. It wouldnt make much sense to do that now before any actual use case exists, then the hooks would remain unused or wouldnt even work properly. Thats why it should be implemented together with a proof of concept plugin.
Its not necessary to learn Rust to improve mod tools in Lemmy. There can be external mod tools implemented as api clients using any language, such as LemmyAutomod. Its also possible to add plugin support for Lemmy, which again can be implemented in various languages thanks to webassembly