ABS works in dirt, front and back. It's job is to stop the tires from locking up under braking.
The problem is that when riding in dirt, there are times when you want that rear tire to STOP spinning because you WANT it to slide. This can actually help the bike turn faster in sharp corners. It is a technique that needs to be practiced though.
Also, if you are just going in a straight line, locking the back tire can actually help the bike stop faster than the ABS would allow. This is because dirt/gravel might pile up in front of the back tire as it slides or digs into the surface, creating more friction than would be available otherwise. I know there have been many times on my 1200 GSs when I have stomped on that back brake expecting the bike to slow down and it just kept going because I forgot to turn off the ABS. However, I generally try to ride such that I am not having to lock up the back tire on the GS to stop. If I am, that is a sign for me to slow down!
I cannot think of any times I would want the front brake to lock when riding on the dirt unless I am already stopped. The danger is losing the front end if it stops spinning. So generally, ABS actually helps in the dirt on the front. There might be some cases, as in steep and rough descents where the tire starts bouncing and losing contact with the ground that the ABS might be a problem, but the newer bikes do pretty well even in those situations.
I had an experience where I was running about 65mph down a straight, WIDE,and smooth gravel road on my 05 R1200 GS. While smooth, it was the big chunky gravel from 1" to 1-1/2" diameter. A turkey vulture came out of the high weeds to the side of the road and I NAILED it! It glanced off the wind screen and hit the right side controls before coming up and hitting my right shoulder and glancing off my helmet as I ducked down. I started hearing an unfamiliar sound from the bike and also the familiar grinding of crunching gravel under hard braking. The ABS was still active because I had forgotten to turn it off. It turned out to be a good thing because the mirror stalk is connected to the hand controls. When the vulture hit the mirror stalk, it rolled the entire control assembly backward almost 90 degrees, causing the brake lever to hit the inside of my hand guard and compress to the full lock position. Without that ABS, my front would have locked at 65 mph and I would likely have been on the ground in a heart beat! As it was, I ground my way to a stop and stayed upright.
Many of the new bikes finally have the option to disable ABS only for the rear while leaving the front active for dirt riding. This gives you the best of both worlds. My 2017 R1200 GS even has lean angle sensors that affect how the ABS activates so that it works better while leaned over in corners. Newer bikes also have traction control that help keep the back end from slipping out under power. This is what all the various ride modes are for. On my old GSs, I had to stop and turn off the bike in order to disable the ABS. Now, I can change ride modes on the fly without the need to stop and restart the bike. This is great!
If you went down the way I think you may have. I really don't think ABS would have made much difference on the front, but it MIGHT have made a difference on the rear. Really, the biggest thing for you would have been keeping your balance on the bike while the rear slid out, kind of like flat trackers do when racing. I found it helpful to watch videos showing top riders going through corners on the dirt. Also, practicing this stuff on small lightweight bikes in a big open field helps. You are FAR less worried about tearing up your nice bike!
I did take a dirt riding class some years back. I did all three levels from beginner to advanced. On the advanced day, one of the things we learned and practiced was driving into a corner, intentionally locking up the rear so that it would slide out, looking through the corner and pointing the front where we wanted to exit, and then getting back on the power as the bike came into line with our exit point. You have to really trust the front to grip and not slide out. This means getting your weight up over that front contact patch to maximize traction. Unless you grew up riding dirt bikes, it is not a real intuitive skill.