Can someone on the higher ranks or a rioter explain this to me?

Hello fellow Summoners, I am currently Plat 1 with a 56% winrate. Now, since patch 9.11 for every win I gain like 18/19 LP and for some reason now losing 20/21 per game when the games are like following: Our Team: Plat 1 - Top Plat 1 - Jungle Dia 3 - Mid Plat 1 - ADC Plat 1 - Sup ------------------------------------- Enemy Team: Dia 4 - Top Plat 2 - Jungle Dia 3 - Mid Dia 4 - ADC Dia 4 - Sup So in this preticular Match the MMR average was D4, so ABOVE my own Rank, it was a close loss since that P2 Shaco was a 76% winrate One Trick was destroying us lategame. So Obviously this Shaco has a very high MMR, and his team was also higher in average Ranked Tier than all of us except the Midlane, which was even. Now, how the %%%% do I lose more LP than I gain on every win, even when we can secure the Win in those games where every enemy is either a super high MMR smurf or at a higher rank. I don't understand it, is this some late aprils fool by Riot on me ala Diablo Immortal? I just wanna understand that system behind this LP loss/gain because it seems total bullshit to me for this patch. Positive winrate 56%, winning a game where enemy has higher MMR + 18 LP, losing against higher average MMR -20, HOW and WHY? Can't Riot just be more transparent with this kinda Information? Because this seems like a Joke to me, weren't they removing the 5th division so people feel more eager to climb? Well thats not gonna work with this kind of LP Gain/Loss on positive winrates while playing against higher mmr than my current real rank. Thanks for any kind of explaination or Info about this.