The key is to not care about rank, or stats, or anything. Once you truly understand it is just a game - you will reach the enlightened place of finally just having fun.
We are obviously past the point where such discussions can influence the course of Halo Wars 2.
But I agree with Dreiga that smurf accounts are very likely one reason why the number of active players is (probably) declining - and nobody wants that to happen.
We shouldn't need to check in the last seconds of a lost game, whether we really just lost against a "RestingLobster7461".
Just to find out a few seconds later, that the last 20 minutes obliterated the 300+ minutes before.
Following your argument, you can just trash the ranked playlists altogether.
In my opinion, the whole problem with smurf accounts is simply the result of a - not yet perfect - ranking system design.
I'm not talking about wasting man-hours on a (probably not feasible) smurf account detection but simply a smarter estimation of the teams strengths.
So considering a game of 3 Onyx players versus a team with 2 Champions and 1 Diamond, why do you lose 20 points on a loss here?
The naive approach would be to simply take the average of the 3 MMR ranks and compare them against the other teams average.
Based on that you decide how many points are earned/lost.
Does this make sense in Halo Wars 2? - Of course not...
It's rather obvious that we're not talking about a linear relationship between player skill and the MMR rank.
The simple presence of 2 Champion players here should lead to a much more careful strength estimation - currently, it (apparently) does not.
I'm pretty sure this could have been resolved by iterating over the ranking system in the same way that we iterate over damage modifiers.
All this needs is a little more transparency when it comes to the ranking system internals and awareness during the development cycles.