Believed people who said miners control the network. Read The Blocksize War and learned how it really plays out.

Similarly, believed a 51% attack gave miners limitless control. Learned later it was only a short window of double spending unconfirmed transactions. (Bad, but not apocalyptic).

Believed TPS fud, before learning that a single on chain transaction can have hundreds of inputs and outputs. And learned about LN and the concept of layered scaling.