It's hard to say exactly what the cause is, but I see two main possibilities: Mechanical causes Brake pads.
If the pads are very close to the rotor when at rest, and have minimal motion to close on the rotor then that may be enough to wedge them.
Try inspecting the brake pads and if worn, replace them.
Brake pads are consumable.
Thin brake pad material will reduce your "modulation" zone, same as hard brake pads on rims do.
Could consider swapping your pads front to rear caliper temporarily as a test.
Pistons.
If your pistons are a little gunked up at the sides, they may not be retracting fully.
This may be limiting the distance that the pads have to travel to be hard on the wheel.
Rotor wear and damage.
Spin the front wheel off the ground and look closely at the rotor—it should not wobble or divert side-to-side, and the friction surface should not have burrs or obvious wear.
Fluids.
I doubt these are the cause of your issue.
Low fluid, or air bubbles will exhibit as spongy-feeling levers and you don't have that.
(edit) though @t_bacon points out that if the system is over-filled it will be slightly pre-pressurised, which will be pushing the brake pistons out a little all the time.
It's definitely worth checking if the fluid is over-filled, by opening the bleed screw and see if fluid squirts out at all.
Technique
When braking, your lever should have a range of motion before the brakes are wedged hard-on.
How tight you squeeze your fingers controls the level of braking effect.
There's a great answer at
What does "modulate" mean when referring to brakes?
Just visualise your flatbar lever instead of road brake levers, the concept is identical.
Body position for fast braking should be "arms straight and arse back" If you try and stand up on the pedals while hard braking your center of mass is higher and theres a moment-of-rotation which robs your rear wheel of traction and imparts a forward force on the rider.
One suggestion would be to swap bikes with a friend and try some carpark laps on another bike equipped with hydraulic brakes, and to get that other rider to try your bike brakes.
Decide if its a problem endemic to your bike vs technique, and go from there.
bicycles.stackexchange.com/users/19705/Criggie
Don't - its dangerous ( Majority of braking force comes from front brakes) and in many countries illegal to ride on the road without 2 operational brakes.
Likely you are using too much force and not enough control.
You need to learn to feather brakes rather than jam them on, while shifting the weight back and lower.
Another possibility is you are using front brakes when you should not be - e.g. down a very steep drop.
If the slope is extremely steep, you need to go in slow, roll it out while on the slope, and brake once it levels out.
Using the back brake only for control can help, but avoid using the front.
Again, weight back and low helps with control.
Its possible the brakes are grabbing, which does make it harder to feather them properly, but this should not put you over the bars.
bicycles.stackexchange.com/users/3924/mattnz
It is unusual to see a hydraulic brake described as on/off, as they are usually well known for their modulation.
However I have had an experience of this before with a friends bike.
He was regularly locking up the rear wheel, and initially I put it down to inexperience as a new rider - until I rode the bike myself and found the brake to be extremely 'grabby' and hard to control.
The problem was resolved by simply bleeding the brake.
bicycles.stackexchange.com/users/14027/Andy P
To answer the last part of your question: yes, ABS systems for bicycles exist (a quick searching of the Internet is enough to see that).
However, they are not widespread and are mostly for OEM city bikes where there are no expectations about rider's skills.
As a result, maybe not something readily available for an end user to buy.
In absence of ABS, and somewhat repeating other answers, here is what I'd suggest to do.
Get better with your braking technique.
Generally the best thing to do is to keep learning about your bike, get to know your trails and to measure your abilities proportionally.
Maybe you are trying to ride features for which you are not yet ready as a rider?
Change brake pads to resin type, if you have metallic ones.
Metallic brake pads have higher grip.
Change front rotor size to one smaller.
If you have 180 mm, go to 160 mm (if your fork is compatible with smaller discs).
Adjust leverage of your brake lever to make it less pronounced.
Only few high-end levers have this option, however.
Change your front brake to a less powerful or try different brake vendor.
Do you happen to run downhill calipers on an XC bike?
Some people feel like a Shimano system is more intuitive to use than SRAM's, others feel like Magura brakes are too powerful, and others disagree etc.
Even setting up a mechanical disc brake can be a thing.
Think again though if trading stopping power for a sense of security is worth it.
bicycles.stackexchange.com/users/26917/Grigory Rechistov
Different brake pads have different amounts of "grab.
" You may consider changing the type of brake pad you use in your disc brake.
Sintered or metallic pads are generally considered to have less initial "bite" than organic pads.
bicycles.stackexchange.com/users/40556/Greg
This feels like something is not quite correct with the front brake.
Sorry, I've missed if you've provided the make/model, but theoretically, modern hydraulic disc brakes should allow complete modulation through the braking phase rather than an all or nothing approach.
That suggests contamination, sticking piston(s) or calipers, etc.
You could also check your riding position.
Placing your saddle backwards a few mm, whilst retaining comfort, would place your centre of gravity rearward, meaning pitching forward is reduced.
This can also be obtained by lowering your saddle slightly too, again, within the confines of comfort and efficient riding.
bicycles.stackexchange.com/users/45199/Lucero79
I am thinking about disconnecting my front brake altogether because it's either on or it's off, and there's no in-betweens. As a result I've been over the handlebars about five times now and it's getting to be a bit of a pain.  Does anyone know if its possible to soften the brakes so the front acts more like ABS?
Front hydraulic disk brake is too powerful on MTB — solutions?
bicycles.stackexchange.com
<brakes><front>
bicycles.stackexchange.com/questions/64580
bicycles.stackexchange.com/users/45617/William
IF a front brake is too powerful it may be the rersult of a number of things. It could be a fault of the rider, who is jamming the brakes on rather than feathering them. It could be riding position, in which case lowering the saddle and moving it backwards may help. Finally, there may be a problem with the brake so the brake pads, pistons, rotor and calipers should be checked. However, the front brake should not be disconnected as it is illegal to ride on roads without 2 brakes. Don't disable a brake — this may be illegal, and it is dangerous. Instead, you may need to work on correct technique and feather brakes rather than pulling harder. Shifting your weight backwards and lower will increase traction on the rear wheel and reduce the chance of pitching forward. Disc brakes should allow for a full range of modulation, but some brakes have more grab than others. Check for worn brake pads, dirt around the pistons and misaligned or worn rotors, and compare with a different bike to ensure that this is an issue with the bike rather than technique. You could also change the brake pads, reduce the rotor size or adjust the leverage of your brake levers.
Disc brakes should allow for a full range of modulation, but some brakes have more grab than others. Check for worn brake pads, dirt around the pistons and misaligned or worn rotors, and compare with a different bike to ensure that this is an issue with the bike rather than technique. Don't disable a brake — this may be illegal, and it is dangerous. Instead, you may need to work on correct technique and feather brakes rather than pulling harder. Shifting your weight backwards and lower will increase traction on the rear wheel and reduce the chance of pitching forward. You could also change the brake pads, reduce the rotor size or adjust the leverage of your brake levers.