How can I get my toddler to eat more?

I am struggling to get my 3 year old to eat much of anything besides pb&J sandwiches, fruit snacks, cereal, applesauce, and fruit cups. It’s mostly just junk food/snacks. For example, I made some spaghetti for dinner tonight and he refuses to eat it. The only other thing he will eat besides a snack is chicken nuggets and French fries if we do fast food for dinner. It’s super frustrating because my hubby and l think it’s so important for him to have a balanced diet but it’s just not working. Any tips??