Ranked is not a mechanic designed around getting "rank up points," it's about getting appropriately matchmade. Playing matches to dynamically determine your skill level against other players. Ranked does literally nothing for a playlist where you face AI, as at any particular moment you can go to Skirmish and do a 1v1 vs the AI to determine your skill against them. It would be like... the participation trophy of ranked...Determine my skill Level against other Players? Well since i got matched against everyone from non Ranked to Champion, the whole System is a joke
The last time you played ranked was like 3 months ago, and you did like 10 matches with friends who were unranked, so of course your matches will fluctuate considering their placement was still being determined. Most of them were fairly well matchmade at that. In fact I went through every page of your available match history (About a year) and counted maybe 15 ranked matches (Though its recording is dubious as there needed to be at least 10 more for it to make sense in the most recent case). The matchmaking system seems to work pretty well when not at either extremity. A 1v1 silver smurf I have that I do dumb things on generally gets put against other silvers, golds, and bronzes. When on my main originally working from the initial diamond up into onyx I was getting what you would expect, mostly diamonds, a few platinums and onyx's, and occasional champs. Onyx/Champ players in 3v3/2v2 generally have poor matches because there simply isn't a large enough population of peer teams, but I also watch a lot of lower ranked streams and they generally get decent matches the majority of the time. However, even in the extreme high end skill cases, whenever two high end teams are searching it pretty much automatically matches them.
Other issues with Vs AI ranked is, even if the difficulty scales with rank, how do you adjust that with varying skill teammates? The answer is you can't very effectively and instead you can just, you know, go to skirmish and tweak the difficulty to your liking that way. I do wish they had an "automatic" difficulty like in the original but that still wouldn't translate well to "ranked."