As others have said, periodization.
OP, how fast are you and how old are you? With better training than 20-30mpw, I bet you could be faster. A good example is to look at how most elite athletes, top college programs, and top training groups are doing things. I guarantee you none of them are doing just 20-30mpw with intensity and getting by because there are no shortcuts to optimal training and performance. You need the aerobic strength, from those higher mileage weeks, long runs, and tempos (**While still touching on speed, form, and strength) to help you be able to do the intense workouts later.
That said, yeah you correct, you wont race as fast unless you are doing the nitty gritty of getting in faster reps, but there is a time and place for everything.
Again, as others have said on here, periodization.
Im not advocating that you run 100+ MPW, I know that different people racing different events respond to different types of training, but if you are training for anything that requires you to be strong aerobically, then yes, you will need more running than what you are currently doing.
Even guys who were 800 specialists like Nick Symmonds run up to 70mpw. Do you do it all year long? No, but if I recall correctly, even in his competition phases he was still running 50-60mpw compared to other elites who put time in between 80-120mpw for the track.
So in conclusion, though it may feel good to run 20-30mpw and do hard workouts, you need to 1) Run more 2) periodize your training 3) understand how training works and that all facets of it add up to you being faster.