Speed is the only thing that matters in time trial. Notwithstanding that, power is your currency to buy speed hence the more power you have the more speed you can buy for your cost curve. And you can improve your cost curve such that speed is cheaper to buy - less body weight, more aero equipment, better position, faster tires, less difficult terrain and wind conditions and lower air density.

We have a local time trial corse and typical speeds on a flat 20k course, low wind and smooth pavement for women are 24 -27 mph and men 24 to 30. And the racers are pretty optimized for time trials. Of course, the speed may be slower.

If your are getting 23 mph on a flat course with 180 watts, you are doing good. There is no way I can generate that speed for that power. 180 watts generates about 20 mph with everything optimized and in my fastest tested aero position and creeps up to more like 195 - 200 watts with a training versus race setup. At the indoor velodrome 20 mph is more like 170 watts depending.

My purpose for the discussion is can you believe the metrics that you are getting?

Your power looks low for the speed but depending on gender / stature, may be okay.

For training, follow coaches advice and ride a lot on your TT bike. I like to do most of my hard interval workouts on the TT bike and save endurance riding for my road bike. If you want to ride 100 miles on a TT bike, you will need a lot of saddle time in the TT position.