I don't agree with this because, in the last decade, Bitcoin's price has managed to touch new heights and went up multiple folds because it wasn't priced very high in the initial days and years, but now, the price has already become very high and for it to gain multiple folds from here or after this bull run, the price will need to touch millions and that doesn't sound realistic to think about.
You are right though that one shouldn't be considered a fool for investing even at current prices if they are investing for the long term because we all know and Bitcoin has proved it multiple times that investors that hold their assets for long-term tend to become profitable eventually.