hate to break it to you guys but making money off of ripping off games has been a staple of the game industry since it's conception. Not only is it a thing that has been practiced time and time again, it has actually been beneficial to the market as a whole. By providing an alternative game play style, artwork, or a specific niche that another game that is similar enough it creates variety. It also allows for the developer to further develop their game to a different direction, because the actual player-base may be much different. As games are ever more persistent worlds, that is there are constantly new updates, - and more so than ever in Mine craft and mine craft like games - they start further and further diverging in similarity.
I mean, no better example of this is the MMO genre and it's history. One can see where a game rips off another game, such as how WoW is being ripped off frequently, and it itself ripped off a lot of stuff from previous MMO games. However each and everyone of those games, whether a success or not also provides an alternative style of gameplay or artwork, or world and adventure to enjoy. Is WoW still the massive MMO giant that it is? Yes. Have other MMOs ripped off WoW and succeeded? Oh absolutely!
Furthermore, think of it also in terms like this, WoW unleashed a floodgate of the MMO genre unto the common masses. Prior to it only a handful of MMORPGs ever exceeded even 500,000 subscribers. Prior to it the MMO genre was a small niche that was slowly growing. WoW blew that out of the water by introducing them to the MMO genre as a whole. This has been absolutely beneficial for other MMOs as it increases the potential player base.
And if you really want to start talking about rip offs, I recall in my childhood playing with something that started with an L and ended with Ego that composed of nothing but blocks and pieces that I can craft my own world with. But now I get to relive this experience on a digital level.