If you make your own salad you can leave out onion and lettuce - I'm not very keen on lettuce myself and I'm veggie! I prefer rocket BUT you can do what I call a "chunky" salad with no leaves - cucumber, peppers, sweetcorn, carrots, mushrooms... Just diced in a little dressing
I make my own passata based sauces for pasta, stir fries, curries,
casseroles and stews - dead easy and easy to "disguise" veggies in - doesn't have to be onions - celery, broccoli, spinach, courgette, aubergine, squash... Lots of mums do this with children that don't like veg. Once mixed in and flavoured you probably won't even notice.
And don't be too hard on yourself most of us stick to favourites. In my house that tends to be:
baked beans, peppers, mushrooms, sweetcorn (inc baby corn), broccoli, spinach (frozen - I sneak into soups and sauces - dd would swear she doesn't like it and never has it 😂) carrots and butternut squash.
Remember too there are things made from veggies like houmous or salsa and they can even be used in cakes - carrot cake or using beetroot in choc fudge cake (makes it lovely and moist).
Dd is quite weird in that she's really not keen on potatoes especially chips/fries. She'll very occasionally have them as mash or roasted but carbs tend to be pasta, noodles or cous cous.
Also I like courgettes and aubergine but they don't freeze very well and as dd doesn't like I don't get them often.