Selling at price with all time high is great way of taking the average potential profit, but you should have to consider that day trading isn't an easy choice. These days while $8k level starved to reach the highest price, maybe we need to wait at least $10k this year until December ends. Long term trading preference would be our best chance, in order to somehow recover our loss.
A smart trader can still make profit from these little fluctuations as a short term trader, just that the trader must be a very careful trader who knows how to analyze the market on a daily basis, not everyone that you see making money have to wait for Long-term investment before they can make money now. Long-term trading is actually the best way of investing in bitcoin which I would not argue that with you, but that is also not to say people should fold their arms and loose the opportunity in making money with all these little fluctuations.
Is someone telling me that if bitcoin does not rise to the level it will become profitable for Long-term investors in 10 years' time, people will still not be able to make money, fluctuation sometimes can be very good, it gives people the opportunity to be able to meet up with their needs while waiting for their long term investment to yield some results.