Normal MMR and ranked MMR are different.
You are way more likely to be matched with players of your own skill level in ranked. That being said, it can often feel harder as everyone is going to be trying their hardest to win and are more likely to be using comms.
The way Riot see it:
** HOW DO I KEEP ENDING UP IN GAMES WITH PLAYERS WHOSE SKILL LEVEL DIFFERS GREATLY FROM MY OWN?**
There are a few factors that can make a match feel more imbalanced than it actually is. A teammate may have just had a bad game and performed worse than they usually do. Alternatively, as we’ve seen in LCS, snowballing can still occur despite the two teams being very evenly matched. Snowballing can then lead to the very reasonable perception that a mismatch occurred. Finally, both the Dunning-Kruger effect and negativity bias also play a role here in shaping players’ impressions of their matchmaking experiences overall.
For the matchmaker itself, the conditions often cited for mismatch are low concurrent users (CCU) or having a very high MMR. But when we take a deeper look at this pool of games, the impact on the quality of matches ends up being very, very low. Instead, the matchmaker is much more likely to increase the queue time as can be seen in the longer queue times seen in the Challenger Tier.
That is not to say that our matchmaker is absolutely perfect. We are also constantly monitoring our matchmaker and making any necessary tweaks to help reduce the chance that players of vastly different skill levels are matched together.
SOURCE - actually a really interesting read
I feel your pain that a lot of soloq players are out there focusing on kills rather than objectives (the main goal of the game is to kill the nexus, not have the best KDA). This issue may have been exacerbated by the recent introduction of hextech crafting and the reliance of good KDA (among other things) to get a chest.
I have had this issue a lot in the past, and actually started off this season with a 10% win rate. Luckily, I found myself a pre-made group, where I am able to freely communicate, target objectives, learn the play styles of my mates (so I don't have to keep changing), as well as cash in on the extra IP, mastery points and hextech stuff. My win rate is now 54%. I would suggest you look into doing the same.
Good luck, may the elo be ever in your favour ♥
