Have i challenged the Halo gods of sweat?

I‘m a big Halo fan, i‘ve played every campaign since CE but i‘ve never got the hang of the multiplayer.
I‘ve played local matches back with CE, a bit of Halo 3, Reach and 5 (yes 5!).
During the flights and at the beginning of the “beta” i had a lot of fun with this game, but now i’m constantly getting pooped on and i don’t even play ranked matches and it’s starting to get a wee bit frustrating (I’m 60 hours in, i think).
I play on xbox, my aim is OK, i know how to handle the majority of the weapons (the ones i don’t know, i leave to guys who do) but sometimes the game seems to play by it’s own rules.

God-like Halo Pro’s on the enemy team ohk me with almost everything, i’m getting gang “handled” all the time, Fiesta blesses me with the Ravager / Sentinel Beam combo, player collision doesn’t seem to exist and melee kills don’t seem to work. Well for me at least.
My team doesn’t want to play the objective because racking up kills seems way more fun (it kinda is doe…).

Like i said, the flights were great for me and i started thinking that Halo Infinite might be the first Halo for me to play consistently. But over the last couple of matches, the skill ceiling went waaaaaaaay up and i’m really curious as to how the match-making works and if other new players experienced the same things.

Maybe Halo veterans can give me some advise as to how i can make this more enjoyable (don’t you dare “git gud!” me…)
Is finding a good team to play with the key?
Do i need to be proficient with every weapon, or should i stick to two or three and learn all the ins and outs?

Other than that, i’m enjoying Halo Infinite and i can’t wait for the campaign. I think 343 did a great job so far. Ok, some things aren’t going so well but overall, Halo Infinite takes me back down memory lane, but with a super car, instead of a rusty old bicycle.