> I've seen "Why don't you do X" phrased in a variety of ways, and the best phrasing I've found seen was along the lines of "I would normally do X in the scenario you've described, but Y was obviously better for your use case, would you mind sharing why?"
There are multiple assumptions in that question that could make it crash and burn really badly. What if they actually didn't consider X? What if they do think Y is better, and X is interim? What if they had a lazy reason to prefer Y, and interpret the hyping up of the quality of their decision as calling them out?
Of course they're assumptions. They're assuming that the person doing Y did so in best faith and full knowledge.
As opposed to assuming they're cousin loving inbreds who did Y because they hate every computer scientist ever.
Assuming that doing Y was indeed wrong, and you want to correct that... do you think approaching it with the mindset of "you're a competent person who made the best choice you could see" is going to work better or worse than approaching out as "you're so incompetent, I've met more capable toasters, and you obviously did this because you hate America"?
It's just people skills, my friend. Start your disagreements by assuming the best of your opponent.
Why are you pretending those are the only two options?
And why is this an "opponent"?
How about both not being rude and trying to minimize assumptions?
Consider that they probably looked at X, but don't put them into an extremely awkward position if they didn't. And the same for the other things I pointed out.
There are multiple assumptions in that question that could make it crash and burn really badly. What if they actually didn't consider X? What if they do think Y is better, and X is interim? What if they had a lazy reason to prefer Y, and interpret the hyping up of the quality of their decision as calling them out?