Minecraft is still alive and well. Still has hundreds of thousands of players daily every month on the servers. The problem is because there is a mobile app now, people will just pay $7 and play on their phones. Therefore new players arent entering the market.

It's a shame. Some of the things people have created for the MC community are nothing less than truly amazing. For example

My seven year-old boy is obsessed with it. Keeps up with news in the modding community. And the amazing thing is that he's shown me how to do things with it that I didn't even know about (I'm more of a casual player and Dad with responsibilities, obviously).

There are no games that superseded it. Other "sandbox" games are entirely different, with more cautious use of sandbox concept.