If you read my blog, you probably know I'm helping looking after the move to WebExtensions as the way to develop add-ons for Firefox. We've received some positive interactions but regularly face critics and bruising (if not insulting and threatening) comments. It's a tough job right now.
But one thing we hear repeatedly is this: "If you take away my Extensions as they exist today, I will just switch to Chrome"
That's a question that keeps troubling me, because I care about Firefox. Here's some points:
only about 38% of Firefox users have an extension 
some of those add-ons with a large install base are defunct eg Microsoft .NET Helper and Firebug
pretty much all the add-ons with a large install base  already exist on Chrome 
So here's my statement: the vast majority of users could switch to Chrome and get all the same extensions with almost identical functionality . For a minority of users using extensions that do not exist in Chrome, you cannot. My guess at that number of users who cannot switch is well under 5% of our user base .
So some people will complain loudly and argue this is the death of Firefox. Whilst I can see this might cause a switch for some people, I haven't yet seen the evidence behind this statement. To be frank, why haven't you already switched to another browser?
The evidence tells me that Firefox must offer some benefits or value beyond just extensions. In fact it's insulting to all those contributors who work so hard on Firefox to say that extensions are the only thing keeping them from switching to Chrome.
So what does keep you using Firefox?
 Some of these are based on numbers I've seen and its Sunday night after the Super Bowl and I've had a drink so this is might not be completely accurate.
 There are some exceptions here NoScript, DownThemAll etc.
 Some people argue that some add-ons are better on Firefox, e.g: Adblock Plus has more features on Firefox than Chrome. For other add-ons e.g: React Tools it's not the case. Yet others argue that Adblock Plus is faster on Chrome than on Firefox and so on. Short answer: it's complicated.
 Remember all they have to do is switch and install the equivalent Chrome extensions.
 That's my guess. This is a number we are trying to figure out.