Yes, intervals / HIIT are really effective and they consume relatively little time. Being an egineer it's tempting to use this as a base for some sort of 80-20 heuristics and simply say "this is good enough" and cut the aerobics.
But is it? It's definitely better than doing nothing. But if the goal is some sort of performance improvement (specially in endurance sports - cycling, running, etc.), 9 times out of 10 I'd go with what's today called "polarized training".
The basic idea of polarized training is "yes, intervals are definitely useful to push the body further, but only after a buttload of cardio". The routine then looks something like for every one very low intensity, very long duration session a week, there's one or two shorter all-out interval sessions.
The intervals alone would lead to a plateau pretty quickly...
Happy to provide references in follow-ups, if anyone is interested.