Am I really that slow?

Just finished my first lap of the island and really enjoyed it. One downside was being a lot slower than everyone else. I lapped in about 18 minutes while everyone else did it in around 11 minutes. I put in a fair amount of effort so can’t figure out the reason. Is it because I am riding on an unsupported trainer (Tacx Vortex Smart) in ergo mode? Will this change when it is supported?

I’m showing you were using Garmin Vector pedals. Is that not the case?

To take 18 minutes to go around the island you’d need an average of around 80 watts, which is on the very low end of the spectrum. If you think you aren’t really on the low end of the spectrum, it could be a calibration issue with your device.