I watched one of your games, and it was reasonably close for most of it, but I saw a consistent pattern from you that ended up costing you the game: As Zed, you tend to go in first and get focused, sometimes getting kills, often not. This is often just due to lack of vision, but you also overchase pretty hard, which gets you caught out. The main point is that you aren't supposed to be the initiator/diver as Zed, and should be aggressively warding their flanks (without getting caught) so you can find a pick opportunity on their carry right as the fight begins and major CC cooldowns have been blown.
Your warding isn't too great either, which leads to your team getting picked when they blindly facecheck things that they would (foolishly) assume to be safe (bush near your team's wraiths, dot bush near dragon, bush behind your wolves, etc). Warding really should be a team effort, and your support was doing most of it on his own (Thresh).
Your lane phase was fairly good, but your mid game looked pretty indecisive. You weren't really pressuring objectives or lanes, and just sort of sat around in mid waiting for a fight. I know a lot of players do this, but I consider it a losing strategy since fights can be 50/50 until one team has a clear advantage (usually after winning several of these high-risk fights), and those odds are a little too high if that team isn't yours. Your team continued to do this after losing several fights, and towers, which translates into what I call "picking a fight to lose." This just leads to the enemy team snowballing even harder unless your team got lucky in the fight.
None of this is intended to be an attack on you as a player, btw, but just a critique of one game--so obviously it doesn't give me a complete picture, but you can see certain tendencies in a person's play--so you can get some objective, 3rd party feedback on where you might look to improve. As for your team being good or feeding, Solo queue doesn't actually measure your overall skill very well, because W/L is the only metric. It only measures your ability to carry a game. I fully understand how you feel about getting matched with bad players, but your only choices are to look to yourself for improvement, or stop playing. The main thing I saw from your play was that your personal mechanics probably carried you to where you are (and I saw you were Plat last season), but your macro game is what is holding you back.
One last piece of friendly advice: Practice your weaker roles in Normals, or dodge if you get stuck with them in Ranked. You have a very low win % outside of Mid/Top, and that isn't helping you to climb. Dodging is only -3LP, and that's a lot easier to take than the -15 or -20 for a particularly badly matched Loss, especially if you can't carry in those off roles.
and 
so you spike at 2 items with 300 AP and 30% CDR, then keep accelerating. Everything else just flops