People who don’t know anything about crypto will always say something negative about cryptocurrency because they know nothing about crypto, and they are not willing to learn something new; while some people will always criticize Bitcoin because of its transparency since they are always used to centralized system where they can scam people whenever they like while Bitcoin has made it’s transactions transparent enough so that everyone can trace the transaction for reference purposes.
People who are at start with this market can have two most common thinking styles.
Too optimistic about this market, and they lack of knowledge and experience as well as too naive so that they don't think of barriers, challenge and risk in this volatile market.
Too pessimistic about this market, like they think this market is full of scams and they are very fearful so that they have no plan of joining it.
To learn about scams and avoid scams, it's helpful to read
the cryptocurrency scam book.