So you advocate universal abstinence, then? 
See, you've fallen into my clever little trap!
The "normal" way is also certainly intentional, but I think we've drifted a bit in terms of exactly what is intended. They're both intentional in the sense that you are intending to make babies, but in the IVF scenario you also intend to do so in a way that could be considered playing God. I'm not Catholic either, but I'm pretty sure that the main philosophical difference is that one way you're using the system "as designed," the other you're "playing God" and trying to hack the system to get the results you want.
The original assertion was that IVF was a sin because many fertilized embryos were destroyed.
I suggested an artificial IVF system that destroys fertilized embryos at the same rate and with the same degree of intentionality as a real human womb. It's
trying to waste no embryos, but unavoidably, it happens to munch 80% of them.
Would the Catholic Church accept an IVF system of this design as non-sinful, given that it performs with the same failure rate and the same degree of intentionality as a human reproductive system?
You suggest that the difference is not one of embryo waste, but of 'playing God'. If playing god means giving otherwise childless couples a chance to experience the joy of babbies, I think we should play God.