I used to have this problem especially at the start of the season falling from decent elo (s1-g6) to bronze in placements, and the toxicity was actually getting to me. Now I am starting to climb and I credit alot of this to the simple fact of the minute i see any complaing/whining/flaming i type "/mute all" and use pings to communicate. Honestly LoL is not a game about being friends with your teammates, it is about knowing the win condition and executing it, imagine that your entire team speaks different languages, none of you would understand eachother typing, you would rely 100% on pings. There is no such thing as ping spam (okay you can spam on someone to be a douche) as long as it is trying to communicate something, personally 3 pings to suggest something 5 pings to demand it.
Also remember this game isn't your job, if you play poorly or get demoted nobody thinks less of you. Nobody will post on reddit dissecting your CS scores. Another point all ranks/divisions don't mean anything, up until challenger nobody gives a crap if you're bronze or plat, comparing silver to plat is like comparing 2 piles of shit, well this one has corn....it is still an actual pile of crap. (Did not come up with this on my own heard it from the current coach for Gravity LastShadow). Honestly these points should change your attitude, if they don't stop being so emotionally invested into a video game