Congrats to these people who made it, you're great!
If I only had a time machine, I would go back in 2010 and invest in Bitcoin... if this happened, then I could already become a billionaire.

But I really think that in 10 years people will say that they regret not buying bitcoin when it was 40k.

If I were you I would better think about your future opportunities than regret lost chances in your past. Past is gone and you need to accept it. Just imagine your possible profits of Bitcoin investments if you started in December when its price was $20k. Don't think about your past just concentrate on your future.