I had a convo with my elementary kids about this a couple yrs ago.
I explained the difference between foods we eat; there's Cake, Kibble and Crap.
Simply put nobody likes Crap. Crap is different person to person. But you can't figure out what the Crap is without trying things.
Everyone loves Cake. But you can't survive on Cake. So between Cakes you eat Kibble. Kibble is what you eat to keep you alive so you can make it to the next Cake. (yeah there's more to it than this, but this is the way I talk to my kids and even my 5 yo got it that it was a humorous twist on a very basic part of life).
Kibble isn't your favorite, but it's not Crap either. Sometimes it's kinda tasteless and needs some salt or mustard. But it is what it is.
"And since variety is the spice of life, sometimes ma will fix different things for the daily Kibble. All I'm asking you to do is just try it. Not eat an entire plate of portobello mushrooms or a bowl of chitterlings, just try it. If you like it, great. If you don't like it, well that's fine too. Just understand that just because it doesn't taste like Cake that doesn't automatically mean it's Crap."
The night I had that first conversation was the first time I made pork chops for them. They'd never had them and were all about "I don't like it" before it ever reached the table. What they meant was "I don't like it because it's not corndogs. I want corndogs."
And now we have porkchops regularly.