I think if you're dissecting the methodology to understand it, it makes sense. I can't share charts here but the f&g was fairly high for a chunk of 2021 and then dipped hard mid year. 25% of the index is calculated based on volatility. At-the-money IV for 1 month options on BTC dropped from 120 points to 70-80 over 2 months.
That drop in IV and the f&g was also accompanied by the dip from $64k to $30K before going for the double top post Elon-induced euphoria.
Again, clearly has its flaws so i dont completely disagree. But i dont think its useless either.