I don't think it's that they are not suitable veggies as much as they are not preferred or favorite veggies for los. Think about it- carrots are tasty raw or steamed with nothing added but eggplant is rather bland unless it's grilled and it's not a veggie eaten raw.
We started using olive oil when dd was around 10 months if I remember correctly. Our ped said to use it in cooking to get extra fats into dd as she had a bad milk protein allergy so couldn't use butter for cooking or baking anything. I used it in cooking.
Not sure if it's suitable for your lo as your lo is very young, but if I remember correctly, you lo already eats meat and other cooked foods, yes? It might be ok but perhaps check with your doctor first on when to introduce things like oils.