It's still 100% true that if too many people chase the same system, it will fail to produce profits for anyone.
However, Order Flow Trading is no longer a single system. There are 3 complete systems described in the book, and that doesn't even cover all the systems that I personally use. Furthermore, there are quite a few professional traders in the chat, and every one of them has their own unique spin on the concept.
Now, if someone expects to plunk down their $150 for my "system" and start raking in the millions a week later, they are going to be disappointed. The 3 systems I included are no longer profitable precisely because too many people are trying to trade them.
It doesn't really matter though. For someone who is serious about learning and applying the information, the book and associated chat are still a tremendously valuable resource for developing an order flow based trading system.
Hope it helps.