It sounds like you're assuming the Copenhagen interpretation of QM, which is not strictly necessary. To the best of my understanding, initially but not solely from the learned hear on LW [LW · GW], QM works just fine if you just don't do that and assume the wave equations are continuous work exactly as written, everywhere, all the time, just like every other law of physics. You need a lot of information processing, but not sophisticated as described here.

There's a semi-famous, possibly apocryphal, story about Feynman when he was a student. Supposedly he learned about the double slit experiment and asked what would happen when you added a third, fourth, fifth, etc. slit. Then he asked about the limiting case - infinite slits - aka no barrier. The point was, there's never a moment when anything fundamental changes about what is being computed, whether there's a barrier with slits or not.