I will be the opposite and say it was good. I really enjoyed the training plan. I did the build me up last spring, the full version and it was not to tough until the last 1/4 of the plan, then it really was an obtainable challenge.
I liked the structure of it. But as mentioned you have to be vigilant to get all the workouts in. No super flexible in the options.
I only Zwift full time about 4-5 months a year so I did the plan right before summer riding season came in. I thought it was decent and I did gain some FTP. Could it be better in a few ways, no doubt but still worth it IMO.