If Universal began producing exclusively PG-13 rated Minions, Despicable Me, and Super Mario animated films, would you question the wisdom of the decision makers? Would you strongly suspect that they're excluding large chunks of their potential audience and leaving money on the table?
As far as I'm aware, Mario has no rides without a height limit. Which is also very silly.
We can't really say that until we see what kind of ROI EU produces. Even then, it won't prove that an approach that appealed to a broader audience wouldn't have worked even better.
If they don't want to compete for the (incredibly lucrative) family-with-young-children market, that's a choice, if an odd one. If that's the case, however, they shouldn't emphasize IPs like Mario, Dragon, and Potter. Build Fast & Furious land or Blumhouse Island.
By the way, are there any quotations from Uni execs about not targeting the family market? I believe there certainly were in the early years of the resort, but is that still an openly stated policy?