Well, absolute numbers of PRs are not that meaningful (it's easy to open a PR on GitHub and leave it be for ages) and should not be compared to apps neither. we are talking a protocol here -- there goes a lot of design and consideration, any mistakes are hard to revert if both clients and servers implement them.

That said, I think it's best to compare development of nostr protocol to other protocols. In this relation, my impression is that nostr is way easier to contribute to the other procols, say mastodon.

Finally, even having NIP accepted, does not guarantee that any will implement it. Many devs are actually working on the implementation first, and then contributing a relevant NIP. It's more organic like that.