I don't think this video is accurate for a number of reasons. The lobby Ace is in at the beginning of this video is known as the "potato bracket." It's reserved for very young kids, very new players to fps, or people who are potentially disabled. It's not for people who are bad at the game, who will generally be facing similarly challenging competition as everyone else across the different skill tiers under strict SBMM.
I also disagree with his premise that the Call of Duty community as a whole today is more skilled than when the series blew up and everyone was just figuring out the gameplay. Because of the three lane map design and the shift toward smaller maps with all the action in a single frame, the game is a lot less challenging to understand and play. It was a lot harder in MW1 and 2 to memorize layouts, stay alive, and chain together successive kills on larger, open maps with low TTK. Now, it's not a mystery where the enemy is hiding - if he's not at the end of the hallway you're looking at right now, the only other place he could possibly be is the other hallway around the corner. MW2019 (and Cold War to a lesser extent) have moved things back in the other direction, which I'm grateful for, but even now situational awareness does not present the same challenge as it did back in the day.
SBMM just means you're getting fewer games where you completely dominate or get blown out. I still generally have a nice mix of games where I break even, fall below 1.0, and go off. I don't necessarily like the swings - it was very noticeable when I logged on yesterday after taking a day off that I was rusty, struggling at first, then getting into a few matches with obviously lower skilled players, before adjusting again when I got comfortable and started facing tougher competition. But the swings would be even more pronounced and random without it. I overall don't have a problem with this iteration of SBMM because it was way more obvious and pronounced in Black Ops III, which I just went back to and found myself still sitting up straight and trying my hardest to go 1.0, regardless of whether I was just picking it up again or had been back into it after a few days. I disagree that there's no longer a challenge to improve - if you focus on learning the maps and the guns and you're consistently staying above 1.0, that means you are improving and mastering the game as you stay ahead of the SBMM calibration. It doesn't mean you're bad at the game, because the matchmaking would still put you into stricter competition whenever you do well.
My tip to anyone struggling with the sweatiness is just play TDM when you want to relax, because there's less pressure to go all out on an objective.