If you're bored, you're not hurting nearly enough or are not paying attention to what you are doing. You're on the trainer to do a job of work, so pay close attention at every moment to everything about being there. Exact pedal stroke, elbows, knees, head, back, butt, breathing, cadence, HR, speed, hand position, then varying all of these and seeing how that affects your speed or HR. You're not just sitting on your bike, you're training. Every tiniest detail makes a difference. You're only on there to do a specific task, so make every trainer session count.

If every time you go out, you're climbing at least 2000', you're not getting in enough easy rides. Or probably enough high intensity ones.

Note that the tri guy to whom you link is advocating the opposite of what was found to be the case in lab studies of competitive cyclists (post 31): Low cadence training is effective when used in anaerobic intervals. Otherwise, not.
Low cadence interval training at moderate intensity does not improve cycling performance in highly trained veteran cyclists