Finding traction on steep, slippery climbs

Grip on a slippery climb comes from a calm, even load on the rear wheel - not from more throttle. Sit down as soon as it gets steep and slide far enough forward that the front wheel just stays down; that puts your weight where it helps and lets you grip the bike with your legs. Feed the throttle early and smoothly - spinning the wheel only polishes the ground and digs you in. Pick a line with steps or roots that give you something to push against, look to the top of the climb, and carry your momentum up from the bottom instead of trying to accelerate on the steepest part. If the rear steps out, ease off gently rather than chopping the throttle, which unloads the tyre completely. A lower rear tyre pressure (within safe limits, ideally with a mousse) enlarges the contact patch and helps a lot.

A starting point to verify on the bike - not a safety guarantee. Change one thing at a time and check on track.