How do improve to actually climb as a SoloQ

Decided to actually play competitive after essentially only playing QP (I mostly play with my friend on Xbox so we can't play ranked together) and that place feels so much worse than QP in terms of general understanding of the game, however, I have read every similar post to this one and seen the usual "You are the common denominator" so I'm asking how can I improve enough to get out this hell hole known as Bronze.

I would like to play Loki most games tbh but no-one seems to want to play Vanguard so I've fell back on Magneto, the character I started playing when the game first released, so I've attached 2 replays where I've lost and definitely made mistakes and just need help understanding what I could do differently

5087427854 - Game where my backline were being dove constantly and I never could quite help enough

5043036554 - OT game that I think I was too passive on and relied too much on my healers (I also fully C9'd)