You can value bitcoin in the same way you can value gold, real estate or stocks, by making a projection of supply and demand into the future. Yes, that's not bullet proof but that's the way markets work. Can you tell me how much gold will be worth in ten years? Me neither.
Right now. bitcoin is more an asset than a currency but as it is legal tender in several countries and unofficial currency in many others, is hard to argue is not a currency. When two people decide to transact in BTC that makes it a currency.
No, it's not gold, it so much better than the yellow metal. It's easier to transfer, transport, and verify. It's censorship resistant, unconfiscable and transparent. Gold is losing market share due to bitcoin the same way blockbuster lost against Netflix. Anything digital is just better.
Dumb money? Elon Musk, Microstrategy, Ray Dalio, Grayscale, Cathie Woods, JP Morgan and many more billionaires have invested billions in it and they'll never sell. Do you call that dumb money? Do you think you know something they don't or perhaps is the other way round?
Bitcoin is not perfect, there are risks involved and it's going to be a bumpy ride but, nothing else can compare to it as an investment. Staying out will mean losing out on the biggest asymmetric bet of our lifetime. Investing in bitcoin is risky, not investing is far riskier.
Not financial advice