I've just served my 3yo a plate of lovingly prepared pork and veggie ragu with carefully separated pasta and peas on the side (as if anything is mixed there's no chance of him eating it) and he's said 'I don't like that, I want real food' 
I really like food, I'm a decent cook and I really try to prepare things I think he might eat. I was so smug when he was a baby because he'd eat anything and I could make sure he wasn't having any salt/only free range meat etc etc. Now all he wants is sausage and chips or beans on toast.
He's not too bad at eating veggies (albeit a fairly limited range of carrots, peas, sweet corn or broccoli) and will eat all sorts of fruit. But he's so fussy with meat (only really eats sausage or ham) and I struggle to get him to eat anything with protein really - no cheese (unless on pizza), no eggs, not much other dairy, no quorn, no fish, no pulses. He doesn't like anything in sauce. His diet is so repetitive and beige!
Every day I cook simple, healthy things and serve them alongside the things he will eat, but it's so miserable just putting it into the bin (or, because I can't bare that, eating it myself!) His 1yo sister is also very influenced by him - so she's almost as fussy 😩
Have you had fussy toddlers who have miraculously come out the other side? Or is this it forever? Maybe I should just buy a freezer full of oven chips and stop wasting food and time.