If Ethereum is a utility platform and the value of its coin rises, how can it continue to be used as a utility when its used as a store of value?
Most people that buy Ethereum aren't using it, they're trading.
That's the magic of cryptocurrency, it's like buying a stock you could use whatever it may save you. The fact that all of the coins are being used as utility and getting high store value because of it's demand and fix supply, maybe there is nothing wrong with that. Hence, it is one of the best use cases of blockchain.