Firefox, as this announcement shows, is just getting around to freeing itself from design decisions which may have made sense over a decade ago when Mozilla had 'software suite' ambitions but we now know are a liability for something with the security demands of a browser.

It doesn't change your overall point, but I think this part is incorrect. AFAIK abandoning those ambitions was the reason they left Seamonkey behind and developed Firefox.

https://gilbane.com/2000/03/netscape-announces-gecko-adoptee...

Support for XUL addons is being dropped now. That's a long echo.

I'm not sure how that applies. Firefox wasn't magic; Mozilla rewrote their browser intentionally and put a lot of resources into it.

> Firefox started well before Seamonkey was spun out

My understanding of that statement is that they didn't drop the old product until the new one was succeeding in the marketplace. I'm not sure how that impacts what I said.

No no, they didn't. Firefox and Mozilla (and even later versions of Netscape) share the same architectural underpinnings. That's sort of the intent and cleverness of it, it's really an entire system for writing cross-platform apps, with its own 'language independent' component model, gui layer, etc. The things that made Firefox possible also made all-powerful Firefox extensions possible. Much of that architecture is still around. In the intervening years, it's become obvious this is not necessarily a good way to build a browser. Which is why they are dropping XUL/XPCOM extensions. If they'd 'rewritten' it, they wouldn't need to do that.

My understanding of that statement is that they didn't drop the old product until the new one was succeeding in the marketplace.

I'm talking about common architecture, not products. If you're unfamiliar with it, just scroll through this

https://en.wikipedia.org/wiki/XPCOM

If you are familiar with it, I guess I don't understand what your objection is.