Most of them know what exactly cryptocurrencies/blockchain are in detail. But usually the negativity comes 'muh climate change' while having 100x carbon footprint than an average individual let's say in El Salvador.

Other point is that a lot of these folks dislike what cryptocurrencies are used for like decentralization, censorship-resistance, financial privacy etc

Then there are those who are still butthurt that they did not buy Bitcoin when it was $100.