I'm bad at PVP too, but have gotten better over time. I have similar experiences as you, but I personally think I benefit from SBMM because I'm playing with people whose skill level is similar to mine.
I have matches where I do very well & some where my k/d is negative, so I feel like it's been pretty even for me.
I also will not play with my friends who are awesome at PVP, but it's because they hog all the kills! They'll get 23 or more per match while I wallow in the minus. When I play solo I do SO much better.
If I was getting destroyed every single match-it wouldn't be fun & I would never play PVP.
I'm not saying SBMM is great, but I'm the minority that doesn't mind it. Yes, coming from the guy with a k/d under 1.0 - I'm well aware.