Let me flip it around. You said, "I wouldn't build a serious site on top of anything that didn't have some sort of built-in sharding story".
I think the opposite. Most serious sites will never need sharding.
I think the opposite. Most serious sites will never need sharding.
I think your definition is better, and I should've said "a potentially-large site" or something like that.
Every large site on the internet has talked about strategies around sharding. At some point you are surely going to hit the physical limitations of one database on one server.