Eh, part of it is experience and how you approach the game. When I hit 30 and played ranked the first time I got placed in mid/low bronze, and I kinda feel bad for the people who played w/ me in promos/on my way dropping before my mmr stabilized. I think the frustration you're talking about will always exist though bc depending on where you're at in terms of game skill there will always be people worse than you so it will always be a source of frustration.
In season 3 I made gold rank by jungling Nunu and playing support Janna. Janna still had global move speed buff (move speed is so strong in low elo that it was broken as fuck), and Nunu was a strong counter jungler so I was able to put a lot of pressure on the enemy jungle. I remember thinking my Nunu jungle was decent, but I recently picked up jungling again after not maining that role since pre season 4, and I realize a ton of things I was terrible at. I had pretty much just memorized common jungle routes and exploited predictability of low elo jungle players. I couldn't adapt when an enemy played differently than normal, I didn't put down much/any lane pressure so I really just shut down the enemy jungle when I'd win, and I couldn't predict where lanes/jungle would want to roam/gank so I didn't counter gank for shit. Knowing exact times of the average jungle route for certain jungles, being able to consume smite w/ the right timing, building Nunu decently, judging when I could sneak baron/dragon, and timing buffs/dragon/baron (it wasn't auto back then) were all things that few low silver jungles did so it gave me a big advantage, but as I've become better at the game and learned to read the map and other roles better by playing them, I realize how terrible I was at the game back then. I see a lot of the flaws in my current game, and am working on them, but I bet there are plat and diamond players who would see things I'm not seeings.
Similarly, at low silver you play with people who finished placements but haven't dropped to the rank they will eventually bc they got lucky in a couple placements (like that gnar only playing vs ad champs top lane in placements or something) , and you probably play w/ bronze players who are duo w/ mid silvers, or who are on a good win streak. It's frustrating when people who have less understanding of the game are in the same games w/ you, but I think stupidity isn't the only reason for that behavior. I played mostly bots to level 30 on my first account and used super cookie cutter builds and didn't understand certain champs or trade well (concepts like wave control were waaaayyy beyond me at the time). People may not have invested the same amount of time and energy you have into learning the game and too this day I tend not to listen people who are rude about advice (not saying you were, but just a note from games I've played) , and while I'll generally look at improving it in the next game I tilt super hard when someone is like "dude you suck, do this instead you crap player." However, at the same time, when I realized how bad I was I invested a lot of energy in getting better, and I may never be good at the game bc of slow reaction times, lack of attention span, and inconsistency of play if I'm happy or sad or whatever that day, but I like to think I'm okay now (low gold is about 30% on the ladder which is probably closer to 50% when you account for people playing multiple accounts, and decent/average is okay w/me).
TLDR; There will always be people worse than you and always be people better than you. As you get better things that seemed difficult before seem stupid for someone to miss, so try to think of a way to find compassion instead of frustration bc the people will drop in rank if they are consistently that bad, and if they're just having a crap game and playing more stupid than usual they're probably as frustrated w/ themselves as you are (well if they're ever gonna climb the ladder they are).
