Mozilla is not very developer friendly. Gecko uses a two decade old method of RPC, the lib interface (XPCOM based on Microsoft's COM) is about the same age, the

Mozilla is not very developer friendly. Gecko uses a two decade old method of RPC, the lib interface (XPCOM based on Microsoft's COM) is about the same age, the documentation hasn't been updated in a decade even though the code evolved, and I've heard from 2 employees directly that it's not important to them. It's not really a surprise that gecko isn't the primary choice for browser developers.