Look at several of the other intersections in that part of I-20:
Hulen: Designed as a major shopping area from the beginning
South Drive: Residential crossing
Granbury: Major retail area
Trail Lake: Retail/residential mix
Westcreek: Mostly residential crossing with minor service stations
McCart: East side of intersection = retail plaza to the north, TXDoT to the south; west side of intersection = residential area
James Ave/Crowley Road: Major retail area at the split of two major roads
Hemphill: Major distribution center just west of I-35W/I-20 intersection.
In typing it out, it seems that McCart could have reasonably been zoned as commercial on both sides of the street right from the get-go.... but even at that, it was a lazy little residential area on the west side of the intersection for over 50 years. And you can't automatically assume that just because a road crosses an interstate, it will become a busy commercial intersection. Look at South Drive which is sandwiched between two major retail areas- it has remained a residential area all this time with little indication things will develop there at any point in the foreseeable future.
Yet organic demand for more commercial use occurred. I don't see that as a failure in planning (especially for what people knew about interstate-driven development in 1960*); it's just growth-driven evolution.
*In the early-ish days of interstate highways, weird things happened. In my hometown, eight homes remained for several years inside the loop of a cloverleaf interchange after I-90 was built!