Steamed fish? Yuk! Yoghurt? I don't like it! Brussels sprouts? No thanks!
Neophobia, fear of the new, is pronounced in children. They only like what they know. In keeping with playing it safe, their favourite food tends to be something which they get most of the time anyway. The mother's favrourite food during pregnancy and nursing also moulds the eating habits of children. If the mother loves garlic or spicy chilli, the little ones like to eat spicy foods later too.
It's not only children and young people who refuse new foods or dishes, to which they are not accustomed. This behaviour is in all of our genes. This distrust protected our ancestors long ago from unpleasant surprises. But what to do if the kids only ever eat the same things? Do not lecture them. Instead, bet on the "more exposure effect". Researchers have discovered that children only trust something new after it has been offered to them about 10 times.
In other words, don't give up. Keep offering small tastes again and again. The kids will risk trying the new flavour at some point and eat the food enthusiastically.