Duo Q ing with your friend for lot of matches messes up with your MMR ?

I get few good team in a row then I find a good player with I can duo with and after a couple wins we both start losing the game even when we win lanes. our team are just of the same rank but their champion pool is smaller and they don't main a lot of champions. I see this same pattern for a year now, is my theory correct or I'm just bad and can't carry?

I play solo now and I play hard carry champs but in team fights, I always lose and I'm just not good enough to carry them like I used to do like before.

and also I'm on gold 3 and I get a person who just reached level 30 and it's their first ranked game.

and today I smurfed in a bronze account and their skill was same as the ones on gold with the same farm as them.

(really sorry for my bad english)