This is the flip side to Google and Firefox both making their extension much more locked down by removing some APIs entirely and requiring signing and approval. There are reasons to be upset that such practices hurt useful existing extensions that people like, but there's also reason to be relieved they are doing so.
The old extension system while more powerful, was pretty flaky anyway. Every browser update had a good chance of breaking extensions. At least now there is a clear api that can be kept stable over updates.
