To answer the question I will start with a question: have you played ANY new course in the last thirty years with a slipe rating below 113? I haven't.
That theoretical average is not the average at all; as Garrison Keillor used to say about Lake Wobegon, "all the children are above average." 113 is a completely arbitrary number in an imperfect system. You'd have to be an idiot to worry much about the actual Slope rating of the course you're building.
However it is entirely possible to design a beautiful and interesting course that is playable for everyone:
St Andrews
North Berwick
The Loop - I think the slope is in the mid 120's, which is about as low as any of my courses have been measured, and it would still be a great course with a Slope under 120 had I omitted some of the back tees.
Ballyneal, if it had a Slope, would only be above 120 because of the average wind speed. (Pacific Dunes would be nowhere near a 140 slope if Bandon wasn't so windy.)
Many self-appointed good players also appoint themselves to be experts on golf architecture, so they can insist that everyone build courses to flatter their ability. And as Mr Dye once famously said to me (about much better players), if you get those dudes thinking, they're in trouble.
ADDING: I'm not sure what the Slope is for Tara Iti, but I suspect it is fairly low, and yet it is rated highest of any of my courses now, so I am "trending" in this direction.