Anyone one who is doubting bitcoin is an unbeliever to bitcoin potentials and if the person intend to invest in bitcoin with double mimd the person we never get it right, for the fact that bitcoin is highly volatile in nature it is not advisable for someone to invest in it with double mind, because bitcoin investment required someone to be committed and focus for that is the only way you can accumulating bitcoin properly using any other strategies.
Every good venture like Bitcoin tends to have a lot of critics to it's cause, when there's nobody against or attacking an innovation, it sends a negative message about that invention. You cannot force everybody to like Bitcoin, funny enough most of those who used to fight Bitcoin now saw it's value and invested into it. For example JP Morgan once said in 2017 that
Bitcoin is a fraud that would ultimately blow up and same JP Morgan owns about $731,246 in spot ETFs. Signaling he just turned believer.
Nobody comes into a new innovation fully convinced, they always give it a try and increase their conviction along the way, it's fine to have some elements of doubt at the beginning of your investment into Bitcoin, but as you learn more about Bitcoin and advance in your accumulation journey having the long-term mindset. Your conviction and appreciation of Bitcoin would improve considerably.