just finished my ranked placements, the system is broken

i just finished my placements, got put in silver 5. my win/lose ratio was 8-2 here is my kda in the 10 games 4-3-6 8-11-13 8-4-3 10-1-3 3-5-9 17-1-19 16-0-13 20-4-26 14-0-3 19-2-9 how the hell did i get put in silver 5 when i literally carried 7 entire games super hard. On a different account my win/lose ratio was 6-4 and i went negative a bunch of times yet i was put in silver 4 on that account. Riot pls fix ur placement system its complete garbage.