It's hard to predict which out of thousands of alts will go up, but what you can predict is that once a coin went up, it's bound to go down. Like, take the best performing coin right now, Dogecoin, there's absolutely no justification for its price, it has no adoption or promising features, it's pure hype. It's bound to go down, so if you carefully short it with small leverage, you're going to make profit. Obviously, the danger is in the known trading wisdom - "the market can stay irrational longer than you can remain solvent", but still the fact that pumped coins will go down is something that you can rely on.
I hear you and yes at a certain point alt shorter are going to make a TON of money but shorting into these bull runs have wiped people out. Touch to call the top and with days of 10, 20,50% gains you can get margin called before you even wake up for the day. Margin has a place but its not a good trading strategy for most.