This may be personal, or it may be true of others. But for me, potatoes have failed every single time I’ve tried them, almost always from insects. The closest I came to success was the time I tried to grow them in a cage. I’ll never know how well that experiment might have succeeded because someone cut off all the plants down to the cage, thinking they were helping me prune. (After exact directions to cut them back a foot out from the cage. They had become enormous.)
Unless you have a very large garden and time to weed like a madman, I’d avoid vine plants like pumpkins, squash and zucchini. If you do plant zucchini, plant only one.
For me, eggplant has performed beautifully every single year, so it may be a location/climate thing. I’m near Philadelphia. Tomatoes are usually problem free unless we have too much rain.
Tomatillos grow enormously huge with very few fruits, at least here. The season is too short for them to be ready for harvest in the fall.
Sweet potatoes or yams – way too much care at harvest time to have something you can actually eat.
Perennial Egyptian onions – they are cool looking and the idea of them was too tempting. But I have yet to find a way or time that they are anything close to something I’d want to eat. The stems in spring are perhaps the mildest, the rest—bulbs in the ground, bulbs on the stems, the stems themselves—are just bitter!