I don’t feel like I can impact my games

I'm playing dota since 2011, I have ~3500 mmr – this is my honest skill level and I will never go higher.

I play only pos 4-5 and I feel like I have almost no impact on the game outcome. It's like I'm playing against a system, not against my enemies.

Skill difference between core/mid player from different teams is huge, in 9/10 games one of mid/core player solo carry the game, and who gets a better core – wins.

This is my lates 4 games stats (enemy mid / my mid):

1. 19/12/27 betrider – 10/14/14 sniper
2. 5/10/13 alch – 19/7/11 mk
3. 5/7/4 ta – 10/1/5 tinker
4. 11/3/5 bone – 2/6/1 ember spirit

And also I've noticed that once lose streak is comming – I'm always getting core players without a mike.

Is anyone getting even games now? It honestly feels like some games I'm forced to win and some games I'm forced to lose. And there is nothing I can do about it.

PS: I understand that boosters can win games on pos 4/5, I'm talking about playing on my skill level only.