I am a 20-year-old student. Not long ago, I heard a famous cryptocurrency expert in Korea on YouTube.
He said, "Bitcoin investment seems to be late, to be honest. I'm sad, too. I think 2018 was the last chance for ordinary people."
This makes me feel depressed. That expert started investing in bitcoin in 2013, and he encouraged his acquaintances to invest in bitcoin, but at that time he said everyone thought he was crazy.
Honestly, as an ordinary college student, the price of bitcoin now feels too much to buy.. If it's the price of the early 2010s, I might have bought it through a part-time job..
I'm so pathetic and depressed because I didn't know Bitcoin quickly. What should I do?

Hello, mate.
First of all, ignore all crypto experts and gurus, no one knows what is going to be in the future. Usually such experts say what people want to hear, when market goes down they shout "sell it, it will continue going down" but when market grows they shout "Bitcoin is a future, buy it!". So don't waste your time and nerves on watching stupid "experts".
Secondly, it's not late to invest, at least because price recently and now is below the all time high, if you follow DCA strategy (you may google what it s) you have all chances to buy bitcoin with a good average price per coin.
P.S. About current price of Bitcoin (34,630$ per coin) it is on the local top (I assume) therefore if you want to join the market, don't spend to much now, leave more money to buy it after the correction of the price. But don't try to catch the dip, it's impossible, always leave some money for an extra dump. And again - DCA is the best way to collect bitcoin for future with a good average price.
Good luck, mate!