It's hard for parents to understand how a toddler can go from eating everything to barely touching their meals. It's even more difficult for them to understand why kids are so reluctant to try new foods. And without a big picture understanding of why kids eat the way they do, parents are left frustrated and are more likely to make feeding mistakes.
My whole life, I was called a picky eater, but I was always assured that I would grow out of it. My parents had both been "picky" (according to my grandparents), but like most children, they had grown out of it. As a kid, I believed that eventually, that would happen for me too. Until it just didn't.