In general, it feels like games are won or lost by whatever position you're not playing.
- If you're not Top, your top feeds a split pushing menace and then leaves them alone to demolish your towers/inhibitors
- If you're not Jungle, you'll get no ganks while the enemy jungler is always camping you
- If you're not Mid, the enemy snowballing assassin/burst mage will roam rampant
- If you're not ADC, your teams ADC won't know how to right click on towers
- If you're not Support, your support won't buy a sightstone, the team will have no vision and walk into a death bush
Even as a Mid Main I've felt like I could carry better from other positions from time to time. Then I play another position and realize "oh, that other position is costing us the game," and the above results.