Buying and holding bitcoin is the best strategy IMO, but I don't think the same is true for the vast majority of altcoins.  Therefore for crypto trading in general, buy-and-hold might not work out for you if you're holding some awful shitcoins or tokens that have been overhyped.  With those cryptos, I think short-term trading might give you the best chance of making a profit--but it's still risky as hell, particularly if what you're trading has low market liquidity and/or extreme volatility. 

Bitcoin is still the most popular cryptocurrency out there by far, and if you think it's going to have any utility as a currency then it has to significantly grow in price if it's going to be used by a lot of people.  And if you're bullish on bitcoin, I think you'd probably end up losing money if you're just trading in and out for cash.  Lots of people get lucky and time the market correctly....but most don't.

That's probably true, and I wouldn't ignore those words altogether.  The market has a way of wiping out both experienced and inexperienced traders.