Unranked MMR is by default (at the start) aligned on your ranked one (same than offraces btw). So if yo’ure being matched with someone way above your own league, that’s probably not a system problem you’re dealing with here, but a smurfing issue (users who deliberately lose MMR in order to be matched with weaker players). Which, doesn’t seems very fair indeed.
I have made a thread defining, assessing and giving some advices about that very issue. If you want it to have more chance to get to the devs’ ears, leave a comment or a like. I’ll submit it to the devs on the next community feedback. 
I do know as I have practiced in lobbies for some time, a bit more than one year ago. The thing is that 30s or 1’ minute more is the delay we’d get around 3K MMR. If you were a 6.5K MMR, who already has to wait 5-6’ to queue a game, it’ll turn into 5 or 6 minutes more. Which I am not sure would please everyone. 