What's preventing Bitcoins from being accepted as mainstream payment forms? I'm working on a new blockchain and would like to learn what drawbacks of Bitcoin urgently need to be improved

To be honest, I don't see anything that is disadvantage of bitcoin. When the price of bitcoin is decreasing it is not a bad thing, it is a good thing for those people who don't have bitcoin it is an opportunity for them to buy bitcoin because their money is not enough to bitcoin while the price of it is bigger. And bitcoin have a many advatages specially the tax of it, because it don't have a tax.