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.
I would go so far as to say that shorting alts at this moment is nothing but a gamble. There is no serious downward force in the market and shorting a coin then going to bed, nah that's not a good idea. If you do it you should be awake watching exactly what happens and short reactively if at all. If you shorted DOGE in the wrong moment you would have been wrecked already as it made its comeback so quickly.