You're painting with way too broad of a brush. It is not always better and not always worse. E.g. "give me a list of users who made two posts where both posts were created within 1 second of each other" This query would likely blow up on a system which has all the data completely randomly sharded (because you'd have to aggregate all the data centrally, unless you had a complicated shuffle setup (which most dbs dont)) whereas would work fine on a system which has posts sharded by time.
