Of course we won't know. Kind of why it's not worth getting bent out of shape over.
McVay is either stupid because he has looked at a mountain of Stafford on film and just doesn't get that he isn't an upgrade in how McVay wants to run an offense. Or he's smart because he's watched a lot of Stafford on film and believes he is getting a good fit, one that will take his offense to the next level. Or maybe its somewhere in between that fans can find some area to vehemently dislike.
I personally love the trade. I think the Rams did exceptionally well. I am super excited about the season... 200 and some days? I'm like a kid waiting for Christmas in July... marking the days as they go by on the calendar. I'll be disappointed if the season doesn't go well. But I still think it was a good trade. If Goff excels in Detroit, and I hope he does, it doesn't necessarily mean that he would have done well with the Rams.
I'd rather be bold and take a shot if I like my chances than to stay complacent if I don't. Go Rams!