Sure, WR mistakes can absolutely lead to INTs. But at least the QB can account for whether or not the WR is in the correct place before making a decision to throw the ball. So in that sense, the QB still has a substantial level of control over whether or not the INT will happen, because if the WR runs a sloppy route the QB can choose to just not throw him the ball. Bobbles/tipped INTs are the only example I can think of that would be 100% on the WR.
Poor pass blocking leads to the QB having to force things constantly which is going to drastically increase the INT rate, which I'd guess is a more common problem at the NFL level than route running causing INTs.