SBMM based on experience or played matches is abolutely missleading!
SKILL BASED is the main part of SBMM.
This means If you have good aiming and good number of kills and damage you can get tougher enemies.
But if your winrate and K/D drops you need to get weaker enemies again.
Hitrate, K/D, winrate, avarage damage all this factors are a good indication in which lobby you need to be placed.
If you get into a higher lobby every 100 matches, but your hitrate and avarage damage stays the same,
you will end up in a dead end without any possibilty to win or show a good performance.
That's exactly what happens in ranked mode. You get points easily, even if you hardly perform acceptable.
Result is you end up in a long loosing streak and all other teams feel overpowered.
But I had this discussion in another thread and someone else was pretty convinced that the number of played matches influences SBMM.
Maybe this is really true and could explain, why it seem to get worse the longer you play!
Another thing is that SBMM needs to be flexible. After 5-10 matches your playerpool should be weighted again.
So if you had a hard day at work and can't play as good as normal your lobby needs to be lowered.
After 1-2 hours you get better and your aiming improves so you can be paired with a higher level again.
In the good old days of CS 1.6 the grandmother of all shoters I adjusted the skill level by changing the server.
I had the possibility to chose myself, perhaps it would be better if everyone chooses the skill level himself...