That isn't an exaggeration or a strawman?
No, not at all. It's a simple matter of you being matched against players where you always need to try your best to win. This is a simple result the matchmaker not allowing you to be matched against people that are worse than you.
Of course it does, if you are below average for whatever reason like being new or casual. It would be literally bound to make it easier.
That's what you'd expect, but that's the trap of SBMM. The moment it becomes too easy for you, the game sees that you're doing better and increases the difficulty again. No matter how much you improve as a player, you'll never get to the point where you can comfortably beat players, as none will be all that much worse from you.
Not what the OP said they want at all. I wonder why you think of it that way.
I didn't mean to imply that OP would only want to play against worse players. Nor was it a direct response to anything the OP said specifically. The reason I said it, is because the game becomes much more enjoyable if you're at least average at the game. If you're at the bottom of the barrel, you're always fighting up. If you're in the middle, there's certainly people that can beat you, but there's also going to be people that you'll be able to beat.
Once you start to get good you will get matched with people that are as good as you and, sure, they may tend to be people that take the game a bit more seriously since you don't tend to get good SBMM stats if you don't.
How good do you think you'll need to be before SBMM matches you with players that'll challenge you? I don't think that's a matter of whether you're good or not. It's a matter of the algorithm collecting enough data on you to present you with a challenge at the proper skill level.
If you can't enjoy a fair fight I refer you to my 'strawman' noob-stomper comment.
That's fundamentally misunderstanding my point about the advantages of a mixed lobby. Nowhere did I say I was against a fair fight. Everyone enjoys a fair fight, just not every single engagement. You want to play against players better than you to learn from and you want to play against worse players than you, so that you're given some feedback that you've improved as a player. You play against players of equal skill level to challenge yourself at your current level. The different types of engagements add the kind of variety that would be missing in SBMM.
If you can't relax playing a shooter against an equal challenge then that's a you thing, not an SBMM thing
This is yet again a straw man.
Find it stressful to every match have to think hard and make an effort to stay alive?
That's exactly why you don't want SBMM. In non-skill based matchmaking you might have sweaty matches, but you'll also have matches that are relatively relaxed. I don't particularly find it stressful if some of my games are sweaty, but I do find it stressful if all of my games are sweaty.