That video of his previous form begs to differ.
To me, Moga carries all the hallmarks of a decent player coming back from injury after spending a significant amount of time on the sidelines. Prior to 2017, he'd played a total of 7 matches in three years, so he's still finding his way a bit.... IMO. There are signs. He's shown a couple times he has an awesome crunch tackle and a very strong fend. I don't think he's as slow as you're making him out to be. He'd be quicker than Kahu.
Certainly hasn't pieced it all together yet. He needs more time before we dump him to the QCup.
Mead, the only logical replacement for Kahu to shift into centre in Moga's place, still doesn't inspire me as being rock solid enough or a better replacement, just yet.