The TrainerRoad workouts should feel like a challenge depending on the IF (basically around .85 should be challenging and .90+ being rather difficult), but not destroy and crush your soul. If you feel like the workouts are too easy and you’re clearly working beneath the intensity zone you’re supposed to be in (threshold feels like sweet spot), then start increasing the intensity by 2-5%. If you have multiple workouts in a row where you increase the workouts by 2-5% then manually adjust your FTP up that amount. However, not every workout is supposed to feel difficult. Make sure your RPE matches the intent of the workout, meaning don’t increase the intensity on planned “easy day” to make it feel moderate or difficult. For instance, in SSB2 mid volume the intensity of the days are as follows:
Lastly, remember you damage your body training so your it builds back stronger during rest days. So rest as hard as you train to reap the benefits of your training.