How is ranked soloq a test of your skill?

I was high gold for this entire season, finally hit plat a few weeks ago. Games were pretty even, I felt like I was in a good place, losing some, winning a few more, steadily climbing up. Hit plat 3, then all of the sudden the drop. I was losing 3x more than winning, and I mean LOSING. In one week I went from plat 5 to gold 2. Ive been playing this game for YEARS, nothing has changed, im just as good if not better than when I hit plat. How then am I getting in games where NOTHING I do matters? I'll tell you why, this ranked system needs a rework. While I do agree if you are better you WILL slowly climb, but situations where you drop that dramatically for no reason should not exist. There needs to be preventative measures to make sure you arent getting unlucky and have the losing team every time. I have the ability to play with high plat players, why am I playing with low gold players and losing? When I play in these games I feel like its an absolute joke how bad people are, I have no problem playing against them, but we still lose the games. Been 100 threads on this, just had to say it out loud, this ranked system is a joke and needs to change.