I didn't say do them only in the summer. I said to make that the bulk of what you do quality wise in the off season which for a collegiate athlete means summer and Nov-Feb for people who don't over do the indoor season. You assumed that I meant that would be the only time you'd do threshold/tempo and that's not what I wrote. Depending on what event(s) you are focusing on, you may choose to continue them or not. Some people do the Coe 2 x 20:00 or the 4-7 mile threshold while some do the in the form of cruise intervals. That's all well and good to set the table, but at some point you need to mix in Max VO2 work, anaerobic power, lactate tolerance (not threshold for MD), max speed, etc. ..again-the mix of which is dependent on the the events and the what the athlete responds best toward. First work capacity then tolerance.
As an athlete, I preferred to do threshold runs in the morning and then a steady state in the afternoon on recovery day. Many of the kids I've coached couldn't take that kind of intensity for that kind of volume. I could do that and sandwiched by a long set of Max VO2 work and a shorter set which was usually 400 meter paced work. It was very similar to what John McDonnell did with the milers at Arkansas. Sunday runs were steady state and again, I could recover.
Fast forward to kids I've coached and the trick is to find out what works best for each athlete you coach. Some thrive on a steady diet of steady and tempo runs and theshold/cruise intervals in more of a Lydiard type build up where we layered the faster stuff in later in the program. I have watched coaches who couldn't get past the work capacity or the "training to train" phase and their kids were always pretty fit, but never really hit that peak racing fitness. You've got to be able to push past the threshold and also be able to deal with varying paces that championship races often feature.
OP, if you are dealing with a coach who just will not do everything he/she can to improve then I do feel for you. I had such a situation and ended up writing my own workouts from high school through college. Talk to the better runners on other teams and determine if what you are doing is similar to what they are doing. Good luck to you.