Main difference between gold and bitcoin is in its history. Gold as a type of investment instrument has already earned its reputation and status. It’s not just a commodity, it’s a financial instrument that had its use in building and making of history and it’s well integrated, recognized and supported by most government and societies.
We still don’t know what Bitcoin really is and how it behaves. It could be valued 10k times up or down next year and there could be no clear reason why that happened. Bitcoin is not in hands of most powerful companies, people and governments and change of its value would not affect anything but net worth of certain individuals or organizations.
By no means, I think bitcoin is here to stay and it has a very clear future as an investment and payment instrument. But I think it’s really silly to say Bitcoin is speculative as much as other investment instruments.