I mostly agree with what you're saying, but I also think there's enormous value in making easy things be really easy. Even with today's state of the art adding a shard, dealing with consistency issues, adding replicas, etc. is relatively hard. Perhaps not in a computer-sciency sense (all the problems are fairly well understood), but in an operational sense. Lots and lots of work needs to be done even with systems like MongoDB, let alone with MySQL. And once you're done with that, you can't really run complicated queries easily, so you have to solve that problem.

We set out to make these things be really easy (whether we succeed or not remains to be seen). We want the users not to have to deal with these issues at all whenever possible. You should be able to set up a cluster, add shards, and run cross-shard joins and aggregation in five minutes.

Of course once that problem is solved, there are tougher problems like high-performance cross-document distributed ACID, but I think the industry as a whole is relatively far away from that right now. (there are some solutions to this - e.g. Clustrix, but they require specialized hardware which makes it out of reach for most developers)