There are tons of critiques, but the vast majority are bunk. As someone pretty much all-in myself, I think I can provide some genuine criticisms. :
  • Although Bitcoin has weathered many years and appears quite solid, there is a possibility of an unforeseen bug with devastating consequences to trust in the system.
  • There may be a hard fork or soft fork that yields unintended, unpredictable consequences. I believe BlackRock has a stipulation that allows them to choose which chain to use should a fork occur. Is this an attack vector? Don't know.
  • While volatility seems to be decreasing from past levels, it's challenging to predict if this trend will persist.
  • There is significant centralization in the mining infrastructure. Only a few entities control which transactions go into a block. Efforts are underway to address this, but it's uncertain if they will succeed.
  • Many governmental entities likely want to exert pressure on the on-off ramps. I'm not sure if this poses a risk for the ETFs; perhaps it's a benefit, but I believe it could impact the long-term value of BTC.
Although it was I do, I would never recommend someone put in all funds. But at this point, there's so much potential upside it would be foolish to not invest some amount you feel comfortable with.
With so many wealthy people in the system now, they will most likely be pumping their bags and they are certainly aware of the risks themselves.