Is there any altcoin that has so much potential as use case in our lives?
It seems that even major altcoin like Ethereum still struggles with securing stores to be used...
Not all altcoins are created plainly as a currency. I guess Ethereum was not really created mainly as a currency just like Bitcoin. It is a currency but with a certain purpose. Ethereum was built offering smart contract. Litecoin was a currency just like Bitcoin. Monero was also a currency but with a strong touch of privacy. Others are coins and tokens minted for a specific purpose or ecosystem.
Stores are not yet fully accepting crypto. Only a handful of them do. But to the stores accepting crypto, Bitcoin will always be there, followed perhaps by Ethereum or Litecoin.