Long term or you mean short term? What you should know is that trading as means of living is subjective. Not everyone can be successful in trading, so when you see opinion about things, you don't just make conclusions straight up. Try and make more enquiries before you make conclusions else you might miss out on some opportunities. What I know is that trading is profitable in the long run and also on the short run just like the way we are having bull run right now.
When you check Bitcoin volume on any exchanges before now, you will see that there was billions of Bitcoin been traded everyday, that's tells you that there are people that open and close positions on Bitcoin everyday, not just Bitcoin but across all over crypto markets. If indeed crypto is not profitable in the long run, I'm not sure they would have come back and also imagine a trader that has opened position or trade since January, they will be on huge profit now depending on their leverage.
That is true, if you want to be a trader, after a certain point it becomes a very different subject. Lets assume that you do badly, then you already quit because you are not getting a good result and you give up and try something else, most either stop all together or they end up with long term holding instead.
But even if we assume that you do fine, turning 10k into 100k is great, but you can't do that with 10 million into 100 million, not the same thing and you would be limited to only a few coin. If you were to do something different then we wouldn't be able to make as much money as possible and it would not be a good thing if we are not careful. I would say that the best thing to do is just making money from long term holding if you want to make some money from it.