Gonna have to say that I have had a very similar playing experience to yourself. It can be pretty hard to play in my preferred playstyle (being very aggressive) because if I do end up going down it's almost a foregone conclusion that my teammates won't be able to finish the fight.
Now I've heard speculation that the game has something called EOMM, not SBMM. That is meant to make you keep coming back to the game, instead of matching you with similarly skilled players. One example is that they give you an easy lobby for your first game of the day, and it's something I've noticed myself but I almost always win my first game of the day, and then it gives you sacks of potatoes for several games after that to make it so you don't win and get frustrated and that frustration fuels you to keep playing.
Apex as a game has gotten worse over time, like on a fundamental level I feel like. They've introduced a bunch of nice QOL stuff over time sure, but shit like audio issues, all the weird ass networking and connection problems (my average ping over the last 3 seasons has increased from avg 60ms to 100ms), plus all the jitter and packet loss, we covered the matchmaking, plus there always a bunch of new fun bugs everytime they update the game.
I love the game, but I think that's mostly in spite of what respawn does and not because of them.
I 100% believe that the matchmaking is designed to maximize engagement like you say and that it gives you a taste of "what it could be" but then does a total 180 for 90% of a play session.
Like you mentioned, I also tend to have extremely high frequency of "good games" and outright wins on the very first match played in a day. My friends and I had noticed this correlation early on in its life (odds are much better for a win/highly favorable conditions in the first match of a day).
And yeah, I agree that after that first match, it then shifts you into a "cold skid", where it'll deliberately hard skew your odds at any kind of satisfying games (no teammates, way outside of skill teammates, griefers, etc.).
Then it's like
right as you're getting towards your wits end, suddenly it graces you with another game with favorable conditions, almost as if on cue.
It's what I was trying to get at in a post in here the other day when I said solo matchmaking in Apex right now feels "borderline abusive". I meant that it'll butter you up and make you feel loved/high like you never have, but then the majority of the time it is just outright dragging you through the mud. And then, right as you're about to walk out the door, suddenly the game cranks the charm and you feel the high again.
It's almost like being in an abusive relationship. Right as you're psychologically checking out, the game goes "hey remember the good times? don't you want more of the good times?". And boom you're stuck chasing the dragon again.
I love the game too. The core gameplay is incredibly satisfying and IMO, when it's working right, it's the most fun FPS multi on the market right now. But so much that surrounds that core, tight gameplay; in particular regarding MM and server/network quality, is absolutely infuriating.