You’re correct, it’s nowhere near a store of value, what with it’s volatility. And it still falls way short as a medium of exchange. Walmart won’t accept it, nor likely would any grocery store.
The medium of exchange aspect of bitcoin is being developed now, with the so-called Lighting Network, a second layer built on top of the base layer of the bitcoin protocol, which, when complete, is anticipated to be able to transact many 10s of thousands or hundreds of thousands transactions per second, exceeding that of the credit card networks. This second layer is now live on the main net and is usable, with transaction fees on the order of fractions of a penny.
If a store or website doesn’t accept bitcoin, there are many bitcoin debit cards out there that they will accept. However, since I believe that bitcoin is still developing its store-of-value property, it is somewhat foolish to buy coffee or groceries with it. You would be like that guy who bought 2 pizzas for 10,000 bitcoins (years ago).