I have been using Zwift with my MTB. My gearing is 1X so my top gear is quite small compared to a road bike. So I end up riding on the flat parts of the course at high RPM, low speed, and low power. Climbs are fine. What I’d like is some sort of setting that would artificially increase the resistance as if I had higher gears so I can get a higher power requirement (and go faster) on the flats. Maybe increasing the grade being sent to the trainer. And have the setting for the amount of increase be adjustable.
What trainer are you using?
Do you have your difficulty set at 100%?
I’ve had the same problem with 2 trainers- Kickr Snap and Elite Drivo. The difficulty is set at the default. I did play around with it but when in the flat sections and the grade is in the 0% to +/-2% range the difficulty setting doesn’t do very much.
I have also asked for this as an option, i think this is on the “nice to have” list and not a lot of users will use it. so we will have to wait in line, until then you might want to look for a cassette with a 11 tooth small gear or get a larger chain ring.
It is not your trainers fault it is just that you don’t have the gearing to go faster, same as in real life, MB cant keep up with road bikes due to gearing.