The secret of friend plantains, I've read, is using very ripe plantains. They should be dark enough that you are ready to throw them away. Otherwise, they can be quite insipid. I bought the plantains only a couple of days before cooking them, and unfortunately they hadn't ripened enough - so yes, they were quite tasteless.
I served them with sour cream, which is a luxury in Belize, but is supposed to make the plantains taste better. It didn't help much this time, but my friends liked how it went with the meatballs.