I’ve been doing a medium volume polarized plan. Occasionally I think I should go back to low volume, but I’m tolerating the medium volume fine most of the time. The problem occurs when I have a scheduling conflict and I move workouts. The workouts are normally on Tue, Thu, Sat, & Sun. Recently I had a conflicts on Saturday and the following Tuesday. So I moved Saturday’s workout to Sunday, Sunday’s to Monday, and Tuesday’s to Wednesday. Great. Not so much. Then I was doing Sun, Mon, Wed, Thu, Sat, Sun. That was too much. So now I’m debating if I have a conflict, maybe I should just skip the workout. I suppose I could move a workout up if I think I can tolerate it. Maybe moving one would work, but not two? Despite the fact that I had two conflicts in 4 days, the conflicts are relatively rare (1 or 2 a month).
If the conflitcts are rare then skipping workouts is not a problem in the grand scheme of things. I would even say that skipping workout is more benefitial than rescheduling if the consequence is higher fatigue and lower quality of following workouts. If you have to choose, always choose recovery 
Yup, after writing that, I came to the conclusion that skipping is right thing to do. There’s a story behind it though. I mostly use Trainer Road during the winter, two winters ago, I was doing a traditional plan and was very diligent and rarely missed a workout, but I was feeling fatigued a lot. Last winter I moved to polarized and missed quite a few workouts. Interestingly, I feel like last winter still benefitted me more. My raw power was down a bit, but my stamina was up. I feel like there’s got to be a good middle ground, like sticking with polarized, but not missing so many workouts. Thus I was resistant to missing workouts. Probably to resistant.
Instead of just skipping the workout that was scheduled for the day you were busy, you should prioritize the key workouts for the week. This means that you can skip a workout to free up the time, but maybe you have the move some of the workouts around a bit.
During the build phase my calendar looks like:
Tue: VO2Max
Wed: Endurance
Thu: VO2Max
Fri: Endurance
Sat: Threshold
Sun: Sweetspot
The VO2Max workouts are the key workouts here. Say if I will be busy on Tuesday I will postpone everything with one day. The sweetspot workout will be skipped, but I will schedule an extra endurance ride for Monday — this should be fine because Tuesday is now a rest day. And everything will be back to normal the week after.
To add onto @jarsson post, Adaptive Training will also taken into account skipped workouts to serve adaptations to your training plan So, yeah, skipping in this case may be better than trying to rearrange your entire week, and you can rest easy that it won’t mess up your plan.