Score means nothing. U can be 2/10/0 every game and will 10/10 and placed to gold / silver (depends on MMR).
If u were silver 3 , 4 last season , u will most probably get high bronze . Silver 5 u will get placed like bronze 3 , and ofc bronze 1 , 2 placed most probably in bronze 5.
If u didn't play ranked on that account ( fresh account) u will get placed in low/medium silver.
If u have good score / cs and u lose that's because u have no impact on the game (example just make kills dont die farm and never focus on objectives).
Edit: Dont blame the team , blame urself and dont be like "OMG I GOT LOW DIVISION BECAUSE MY TEAMS ARE SO BAD !! I DESERVE GOLD BUT EVERY TIME NOOBS FEEDERS GG BRONZE / SILVER FOR EVER" (Silver mentality)