Loss of LP Makes No Sense

So I just played two promotional matches to get to silver 1, again, and in both I did fine but as usual my team just hardcore fed and screamed at each other in chat the whole time, but that's expected cause that's literally every single game in this ELO, winning requires me getting fed enough on my own to work around that and to calm my team down. Ofc easier said then done while fighting against a team with 4 fed members on it....

The part I'm confused about is even though I did perfectly fine considering how awful my team did from the start, AND that me and my team were all lower rank and lower MMR then the enemy team, I still lost 20 freakin LP for each game! WTF IS THIS BS!? 20 LP lost for a promotional game where I did fine against a full team of higher ranked opponents!? I get that you lose more LP when playing against people lower ranked or MMR then you, but I'm constantly playing against higher ranked people!

Do I lose so much LP cause I'm on some higher ranked teams and carry on them or something? Cause I mean I have a 55% win rate atm in solo Q (95% in ranked teams, go freakin figure) yet I'm still steadily deranking and I'm still playing against people higher ranked then me...... Riot this literally makes no sense... almost as little sense as my placement at the start of the season, cause making me play against plats and diamonds for all 10 matchs and carrying half of them myself definitely deserves me losing 4 ranks......

I seriously think there's a huge flaw in their algorithm for LP loss and gain, or MMR in general, idk but something is seriously screwed up.