To be fair/honest, there are some situations in which the Magic Academy is useful. It's those infrequent, transitory periods when, for whatever reason, you're super low on supplies, or just really want to amp up production of a certain manufactured good—say, to unlock a new technology, or replenish your stock after negotiating for relics—or that extra 5% culture bumps you up to the next level (because again, you're super low on supplies).
Yes, yes, I know—in a perfectly balanced/managed city, one wouldn't go through periods like that. But I have never claimed to be a perfect balancer or manager of cities. So I will freely confess: I have used the spells to good effect upon occasion, when strapped for supplies/goods/culture and feeling especially impatient.
However. I am not a bad city-balancer/manager either. Which means: 98% of the time, those d**n academies—yes, I got carried away and built them in Arendyll and Winyandor—just sit there. Taking up space. And snoring.
Those longed-for combat-enhancement spells really can't come soon enough.