I (kickr - ipad via BT) am also having these problems. I have only done group rides. When we hit the steep climb f.e. in Innsbruck I don’t feel the climb, my speed drops, and I have to ride at a high cadence to keep up with the group. I almost spin out at a high gear. It is also very difficult to keep up in the descents.
I thought I had tot adjust the trainer difficulty to maximum to solve the problem, but it just doesn’t feel different.
This is all very frustrating as for me, without the feel of the climbs, zwift is useless.