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.
My unfashionable opinions about bitcoins are:
1. It can not be used as a replacement of regular fiat currency due to high fee and network load. There are other crypto currency that can do this job better.
2. Better to use it as a store of value than a regular currency
3. No matter how much we deny, it actually helps criminal to stay under the radar.