My brother in law is in a similar boat to you and my sister found some really great recipes in this book below
You can try hiding veg & protein in foods. There’s a book I came across years ago that I think might be helpful called Deceptively Delicious: Simple Secrets to Get Your Kids Eating Good Food
Also, it may be hard for you to do, but don’t offer carbs. My child, too, when given the option, will fill up on carbs and then say she’s full. She’d go for the bread, pasta or rice that I would cook for her as a balanced meal and then wouldn’t eat the rest. So now, her plate only has veg & protein. She can have her carbs after she’s finished the veg & protein. We reiterate that it’s the least important food group.
We regularly offer different snacks. I always have a crudités platter ready to go in the fridge. I pull that out every day to keep husband, kid and I from eating junky snacks. When kid comes home from school, I offer fruit as a snack. I know sometimes, we like crunchy things to snack on. So I also have cheese crisps, dehydrated veggie chips and pork rinds on hand.
It’s also hard to break habits we grew up with. I have a friend who complains that her toddler will only eat potato chips and cereal. Her house has lots of junk food (yogurt w/ m & m’s, fruit snack gummies, chocolate covered granola bars etc.). Who wouldn’t want to eat that? I would only want to eat that if it didn’t have any long term effects to health.
She was seriously thinking about taking him to occupational food therapy like I did with my kid (but my kid actually has sensory processing disorder and had issues with food textures like would only eat raw carrots, not cooked). If kids are neurotypical, then they are just displaying a preference for what they want to eat. If the kid is on target for weight, they will eat what you give them when they are hungry.
I sometimes buy things she likes like goldfish, cheez-its and on the rare occasion fruit snacks. But that stuff IMHO isn’t all that nutritious, but I don’t want to make those foods so taboo that she grows up to eat those foods in secret.