WWE has always been incompetent, so let's continue to give their incompetence a free pass is not exactly a compelling argument.
GUNTHER'S reign being a big deal, which it definitely is, has nothing to do with why Rey losing this match (or being stuck in a go-nowhere program with a go-nowhere geek like Kross) is a bad idea.
If Rey had won the match and then lost to GUNTHER, I'd be a little more okay with that, because 1. it's a compelling as fuck combination, 2. GUNTHER is a big deal, as you said.
Ultimately though, it would've been better for Rey not to be in this match at all.
Yes, Rey is old, but he's still a big star and major attraction. He should be treated as such, so that when he does lose, it actually means something. Having him drop throwaway matches to disposable talent like Kross and Moss is a terrible way to use him.
Hey, that rhymes! Make Kross and Moss a team.
Why not? Can't be any worse than anything they're doing now.