Don't despair, my 2 have both been serious fruit and veg avoiders for no particular reason, and have improved with time. Dd now 6, ate all food until about 2 then really seemed to go off the texture of fruit and veg. She gradually improved until now is pretty adventurous eg: loves cucumber, raw and cooked mushroom, melon, berries, apple, will try some salad. She still has strong dislikes of tomato and banana, but I cheerfully put them on the plate to share anyway, and the odd one slips in. She can tend towards picky and has to be encouraged in appetite occasionally. I fully admit I was really worried for a couple of years, mainly because the amount of food she ate overall wasn't huge and because she is my pfb. No problems now at all with that as she is a tall and healthy girl who naturally seems to prefer unprocessed food. She will try lots of things in school dinners and now eats fruit and veg first off her plate.
DS, now almost 5, absolutely refused to eat any visible fruit or veg apart from potatoes from about 2.5. Huge appetite for spuds, meat, fish, cheese. Would plow through a hot curry and rice or a plate of chips any time. Big lad for his age (as in future rugby player, rather than fat). I had relaxed much more by time I had him and let him go at his own speed rather than stressing.
It helps that they both went to a brilliant nursery which does home-cooked, quite adventurous, food. Once he was about 3.5 and was keen to fit in with all the other kids, he just started eating pretty much everything there, eg: meatballs with cous-cous and roast veg, veg and lentil curry, all kinds of cut up fruit for snacks, pasta bakes with loads of veg, and his absolute favourite is soup served there made from root veg,spuds and celery! It's liquidised so smooth and he will eat several bowlfuls with fresh bread. Texture seems to be a big thing with him too - he loves the taste of fruit and will eat any fruit if cooked in a cake or as a smoothie. He still makes a fuss at home about eating stuff I know he has at nursery, so I just tell him that he's been rumbled and to get on with it! Doesn't always work but I don't stress much.
My secret weapons from age of 3-ish(and still) are a fruit smoothie in a carton with straw every morning, and once or twice a week they have "Daddy's bolognese" sauce and macaroni (easier to shovel in than spaghetti). He makes this in huge batches and freezes, then quick to just nuke some whilst pasta cooking. It consists of a third beef mince and 2/3 veg (passata, tinned toms, bit of ketchup, onions, mushrooms, carrot, celery). They practically inhale it, and still have no idea how much veg is in it. However picky a phase they might be having, if they've had a huge bowl of this with a bit of Parmesan and butter in too, I know they've had sufficient great food to cover a couple of days of whinging. Anything else is a bonus. They both love baked beans, so cheerfully ate mild chilli with some hidden veg and "purple beans".
Sorry for the essay... Just wanted to say it will get better and don't worry!