It works to a certain point, yes, but I daresay that the overwhelming majority of OLTP needs are in the <= TB range, not PB. OLAP is its own beast, though I'll also say that most modern tech companies' schema is hot garbage, full of denormalized tables for no good reason, JSON everywhere, etc. and thus the entire thing could be much, much smaller if RDMBS was used as it was intended: relationally.