Bitcoin is actually the closest to solving the scaling problem, because it has Lightning Network and while it is not yer released officially, people already use it on mainnet. Ethereum's scaling solutions are in much earlier stages of development, and other cryptocurrencies that claim to have solved scaling are so centralized that we shouldn't view them as competitors of Bitcoin - they are entirely different products with different value proposition. This is one of the reasons why Bitcoin is doing so well and altcoins don't.