Many altcoins are created with different purposes. I am not sure why only Ripple is being compared? In reality, altcoins shouldn't be compared with Bitcoin at all. There are multiple reasons alongside centralization. Also I am not against altcoins. There are many benefits altcoins provide.

Bitcoin is more like pioneer in this market and enjoys the first mover advantage. But altcoins are also needed, especially coins like Monero. In this world of surveillance, privacy coins are really beneficial.