Strategies only fail to work if they were only working due to good luck in the first place.
Its possible to spot a set-up that is working due to good luck all this week, all this month, even longer maybe. But eventually, statistical probability outweighs luck and it can therefore look like a good strategy failed. The suspicion is often heard that a good strategy was arbitraged out by becoming too well known and counter-played by the bigger players. This is BS. It was never a good strategy, only a lucky one.
Trend-following strategies work during trends. Range trading strategies work during ranges. In both cases they always have and they always will.