That's by design, that's just how legacy mode works. Like it says on the description when you change modes, legacy is camera based, standard is character based.

I could be wrong, but I'm pretty sure 1.0 used "legacy mode" (it was a long time ago, my memory is hazy, but that would also explain why it's called that) and since it's been like that for 7 years now, it'd just cause issues for a lot of players who use it if they suddenly change it.

I don't know how well this'd work on a controller (I've only done it using keyboard/mouse), but if your only problem with standard is the slow walk backwards, I recommend trying to remap left/right from the default turn left/right to strafe left/right. Then when you want to get out of an AoE turning 90 degrees left/right and strafing the rest of the way out of it.

I'm probably not explaining it very well, but whilst it's not quite as convenient as just walking backwards, it does become very easy to do.