You could probably compile the release version and change anything you want to, but that won't get you automatic updates.

As a fully open source product, with a demand and will large enough, someone could make a fork, even a minimal one, where they take upstream and keep this feature enabled. I personally don't think sufficient demand and will exists for that to happen.

I suppose they could make an about:config option out of allowing it, but really, so few users will probably find it so much of a problem that even a bug report/feature request for that probably wouldn't get traction.

They can't please everyone. Overall, it seems like a reasonable move to me.

You are not entitled to having your edge case supported in whatever specific manner you desire.

They're entitled to complain, though; that's a proper, by-the-rules way to signal preferences to the market.

FWIW, I agree. Having the choice only between casual user version and unstable dev version is missing a power user option in the middle. I'm personally not going to abandon Firefox over this, but I'm that less interested in embracing web as a platform for productive work.

They weren't until Mozilla took away their tools to support their edge cases themselves.

Sucks to be you I guess.

Then you educate yourself on those versions, and discover that the "dev" edition is not a prerelease version at all, unlike beta and nightly, which are. The Dev edition is a version of the main release channel with flags turned on/off to enable all the "only powerusers need these things" functionality out of the box.

Like installing whatever extension you want directly from file.

I think you're wrong about that. My Firefox Developer Edition install has upgraded itself to 71.0b6. My Firefox install is at 70.0.1. Both claim to be up to date...