Everyone has a few. What are yours?
My main ones are - unit bias has held back BTC's progress in the mind of the public.
Bitcoin will never see widespread use as a currency.
95-99.5% of the world does not want to be their own bank. And a decent proportion who do want to be, should not be.
Bitcoin can never become a mainstream method of settlement. Moreover due to its deflationary nature it can't even be used as a national currency. Moreover scaling issues will even hamper its growth as a popular currency. Moreover people are not prepared for crypto for atleast another 20 years so no chance of a good adoption rate. Me myself would not like to spend my money in a type of currency which becomes expensive the very next day as it will make holding that currency a better option than spending it.