With sickly infested plants and not a single zucchini to show for this summer, I've learned the hard way why crop rotating is a thing.

I only have a pretty confined area in which to garden, and the problem is basically everything I want to grow is in the squash family. Is there anything I can do to make the same area suitable for repeatedly re-planting the same family (short of dousing my future dinner in pesticide)? And, is crop rotation entirely about pests or does it also have to do with the soil getting depleted? (Wondering if it's worth buying amendments.)

If I must think of something else to plant there, is alternating every other season enough, or are you supposed to cycle through multiple other families?