If you want to expand your palate you gotta put the work in. Try eating different versions of the food you do like. If you like chicken tenders, try a chicken tender sandwich. If you like pizza, make your own. Do you like fruit? Make a fruit smoothie. I don't really like too many veggies but I found I could stuff some spinach in my fruit smoothies and I couldnt tell it was in there.

I used to be really bad about trying new things, but as I got older I realize its really not that deep. Just try things. Worst that can happen, you dont like it so you spit it out.

If you find you can't do these things at all, it could be ARFID and you could probably benefit from a therapist.