I have the same bike as op riding every day for a year, probably 2,500 miles on it. I think the brakes are good. Not nearly as powerful or controllable as the shimano xt full hydraulics on my mountain bike, but good. I put the difference in power down to the levers and the inherent difficulty braking from the hoods compared to a flat bar, plus the different weight distribution on a drop bar bike, and tyre differences.
My levers move a little more than I would like, but by no means down to the handlebar. That doesn't sound right. I would have a look at the pads, make sure they haven't worn down. I would also try taking a little bit of slack out of the cable, trying first with the barrel adjustment, and then by undoing the hex nut and pulling the cable a bit tighter if the adjuster didn't work.
I can easily skid the rear wheel unless I am careful with the rear. I feel confident with these brakes, even compared to my mtb.
Possible contamination- you can clean up the rotor with some rotor degreaser or IPA and paper towel.. It's worth doing that semi-regularly anyway. I think I have seen some people saying pads can also be rescued, but I can't remember how. Traditional advice is to get new ones if pads are contaminated. Do you protect the rotor when using gt85 or similar on the cassette?
I would start with brake lever travel.