Fiat is worthless now. We just don't recognize it, because we don't know what we would be able to buy with 1 dollar in 1917. And btc would go much higher than 10k.
If it's worthless then we are not using it anymore, fiat just the opposite of bitcoin because the value decrease overtime while bitcoin it's expected
to rise due to the limited supply. However, in terms of practicality, I guess a lot of people are still comfortable with using fiat and that would make fiat
better than bitcoin.