I'm not sure "where I went wrong" but a couple of my kids would never eat a vegetable if I didn't make them.
I don't think I was pushy about it when they were little. I don't think I made them eat too many weird things (ok, maybe a few weird things before I settled down into a more chill mind-set). I don't think I've deprived them of treats.
But still, if I didn't say, "Here's a carrot (with ranch), please eat it so you don't get scurvy" they would just settle down with their non-veggie foods and never even care.
I've been parenting long enough to know a fair amount about picking battles, and the very big truth is that I'm incredibly thankful that their "rebellion" is about vegetables and not about illegal drugs or many other forms of yuck we want our kids to avoid.
A mom of teens/adults must have perspective, and when I look at the big picture, I'm going to say this:
I'm so glad that my kids are choosing Jesus even if they often choose to shrug off the salad.
There are worse battles to fight, so therefore I try not to fight. I encourage, I nudge, and I always provide the good stuff. They do eat the salad, they just prefer the pizza.