I totally believe this as after I have some decent games not only am I in try hard sweaty lobbies but I die in weird ways
I mean I am turning the corner or just moving through the map and I just die in what feels like 2 hits but when I watch the kill cam he sees me long before I see him.
What I feel the SBMM is intended to do for the average player is keep every around a 1 ish to 1 KD and win ratio
So many people I know playing these last couple of years say their kd and win ratios are very close to even
SBMM has been going on more than just servers and lobbies. I think it was MW3 (2011) where guns got really condensed into same-ish performance and maps became rat mazy. SMGs got a big improvement to recoil so you can kill people from distances no normal person could with consistency. There is no way anyone with MP5s, MP40s, Thompsons etc... can pick off people like AR/LMG in old games. But now any noob can run at Usain Bolt speed, unlimited stamina and spray rooms.
The SBMM trying to get people into 1.00 ratio tiers goes beyond competitive games. It equates to money and mtx. The more people stick around to play (most people are lousy at COD IMO), the more they play and the more mtx they make as casual are surely buying skins and loot crates. The hardcore gamers that really care about WL and KD ratios are the minority. If they drop off, they wont care.
When I'd look at my friends leaderboards for any COD game, the people that generally played the least were the people bad at it. So they bailed. It's not too often you see someone with decent or good stats bailing right away. Now Noob Nancy might stick around if she's put into bottom tier SBMM lobbies. And now she feels good getting 1.00 ratios with the rest of the bad players. Now she might buy a Lara Croft skin.
The best example is Apple transforming from rebel with weird specs to trying to normalize Macs for everyone, even using Windows and MS Office if they want. For every nerdy Apple rebel from the 80s and 90s they lost, they probably got 1000 casuals buying their stuff now. There's a lot more sales catering to the masses than the hardcore gamer.