If BYU had beaten Cal and USU, we'd be ranked, and I think most people would be clamoring that independence is working. When the product on the field falters, we start looking around trying to figure out what to fix.
The only only argument that's possible to make is that BYU's on-the-field performance would improve in a G5 conference. Bronco used to talk about how hard it is to prepare fresh for so many new opponents every year rather than being able to lean on last year's research for conference opponents. Maybe BYU would have more success with regular opponents outside of Utah, USU, and Boise. Who knows.
Also, there's an argument that BYU would fare better by dumbing down the schedule. Maybe. It's worked for other schools. I'd rather play the best competition personally, but I understand that's not for everyone.
I don't really feel like recruiting would pick up in the MWC or AAC. Maybe, but I don't think so.
If BYU goes from being a #50-something program in independence going to a bowl we've never heard of to being a #50-something program in a G5 conference going to a bowl we've never heard of, I don't think it's going to make anyone happier.