ellie97, it's heart breaking when ducks don't respond to our friendliness. But it's not hopeless. I found it took hours and hours and loads of effort, but we got through their adolescence (when they acted as if I were the runner duck axe murderer) and some time later several of them began to let me easily pet them and pick them up, and all of my ten runners are very sweet and friendly and cooperative, though some of them are still a little shy.
Peas (thawed from frozen, or fresh) helped quite a bit. So did recognizing the things that scare them. For a while, anything coming at them from above sent them into panic. Singing lullabies every night can help (I'm not the only one who does that), routines, and just time near them. I mean, serious time. Like, at least half an hour three times a day - if you can spend an hour sitting with them - just sitting with them - it will help. You might try sitting in a safe space (no other people or animals, no loud music or TV, just you and the ducks), with a cup of peas. Roll a few peas toward them. Wait. They may take them, or not at first, but most ducks (not all) love peas. Perhaps say a special word while you're giving them peas.
Each time you give them peas, place the peas a little closer to you. Eventually, put the peas on your legs or right next to you, put some in your open hand on the floor. Resist the urge to reach for the ducks for the first few times you do this.
I used to sit in the brooder pen after cleaning it out and just let the ducks pull on my clothes or sit on my legs or pull my hair. When they were about three weeks old, they became terrified of me. So I had to start all over again socializing them. But it worked, and now I have the best flock of runners ever (IMHO).