I’m sorry you feel that way about gatekeeping. The members who have been around longer can be more jaded, sometimes rightfully so, sometimes they need to touch grass. Your question is reasonable and you shouldn’t feel bad for asking!
As someone who specializes in trophy cards, I didn’t know what they were when I started collecting. I got back into pokemon about 20 years ago, and started with wotc and the cards I grew up with as a kid. I moved onto the newer cards like gold stars. Once that was complete my hunger wasn’t satiated, and I discovered Japanese promos, and finally trophy cards.
Outside of my experience, I think trophy cards objectively fit the term grail better than any other card. It’s why you see people use the term so loosely, both grail and trophy. They are the top of the mountain in collecting pokemon. There isn’t another card category that combines rarity, history, and exclusivity like trophy cards. It’s why the illustrator is the most valuable pokemon card.