More precisely, enjoys memorizing things but isn't good at it. Professonal quizzers can absorb huge amounts of information but typically don't use flashcards. OP is grinding thousands of cards a day to get to the same level - worthy of respect!
Professional quizzers almost all use flashcards. Jeopardy! people definitely do. The range of questions that you can ask in a general knowledge quiz are surprisingly limited. You're not going beyond a surface-level overview on anything. Do a ton of general knowledge flashcards for a year and you'll annihilate people at pub quizzes.
I suppose you could just read encyclopedias over and over again, and books of lists.
Reminds me of that guy who "mastered the NYT Crossword" by flashcarding questions/clues. I also learned to do the Saturday consistently - just by doing the crossword every day for a while. You don't always need flashcards.
Can you elaborate on this? I watch an unhealthy amount of University Challenge and I assumed that the vast majority of contestants would use flash cards as a trivia retention tool. Most people I've met who need to rely on large amounts of accurate but relatively dispersed knowledge (law students, say, or specific historical professions) use flash cards in one way or another. It surprises me greatly that 'professional quizzers' wouldn't. Perhaps _some_ of them wouldn't - I'm sure as with anything there are some who are preternaturally excellent.