Everything was fine until we read that message today. I concur to the other reviews.
To the developer and who ever may agree with their rant:
You have zero understanding of security unfortunately. Forcing 2FA is not meant to force *YOU* into being more secure. It is in order to guarantee the safety of your *USERS* and by proxy Firefox's users. If your account gets hijacked, your addon can be used to hijack user's browsers.
2FA makes sure that YOU are the only one updating an addon. And also it removes any "plausible deniability" in case an addon has been found to do something questionable. An author can't claim "my account was hacked hence I didn't add that to the code".

It is in EVERYONE's best interest to enforce 2FA and you have no right to refuse security to millions of users with such a moronic excuse that has no merit at all. Enabling 2FA on your account, all it needs is a SINGLE email address. No other information AT ALL.

So we can safely conclude that the author addon specifically does not want to enable 2FA on his account for malicious reasons or he's a complete idiot who did not bother to even check what the process entails and also has zero understanding of security concepts. In any case an audit of the addon's code is in order and we should look for alternatives anyhow as after his statement we have exactly 0 trust in the author.

EDIT: This is a reply to the developer's reply. The world has ALWAYS been wicked. From its inception. It is exactly for this reason that security is required. You may be fed up with the state of the world, I am as well, but this has nothing to do with this particular case. If anything, enforcing 2FA on addon uploads helps REDUCE the effects of the wickedness you're talking about and your stance is literally opposing this. Intuition means nothing in this particular case because it's as simple as 1+1=2 and that's non-negotiable fact. It's not something that your intuition may later on prove you correct or anything of the sort. The facts are these:
1) Addons, through their legitimately required for functioning permissions, provide an attack vector for mallicious users.
2) If someone gets access to your account, ALL your userbase is made vulnerable to the attacker.
3) By enabling 2FA on your account you make fact number 2, extremely more difficult to occur.
4) By enforcing 2FA on all addon authors you literally protect millions of users using addons.

It is that simple. So it all boils down to:
A) Do you want millions of users in increased danger because you don't want to provide a single email address (that you may even just use for this reason alone and nothing else) just because your "intuition" tells you otherwise, defying all laws of logic and reason?
B) Do you actually want to help the web and millions of users' devices be safer and more private by making an effort to understand why and support this change by doing something as simple as adding 2FA to your account?

The choice is yours. Make no mistake, this is exactly what you're being called to choose. There are no buts or gray areas. It's either A or B.