Correct
You chose not to have four teammates
You chose to play the format where this isn't an option or chose to waive your right to a full team
You have a 60% winrate, at the end of the day the system is working in your favor.
- If the system works how it appears to then you will advance at the rate of someone who wins 60% of the time
- If the system is geared to tilt you for winning too much then the same applies to everyone else. You will be matched against the same thing as everyone else in your situation and will advance according to your skill regardless
No matter what you will advance as someone with a mere 60% winrate should. Be thankful that even with your being too lazy or unappealing to proper teams or simply aren't taken seriously by those who really want to get ahead that you can still manage to win 60% of the time and remember that every now and then you have been matched WITH others in your situation and you have been that very same piece of shit you pretend is holding you back.
It is your fault that you lose. It does make sense to team him up with you. If you would like to use a different system then have the balls to just say that directly instead of bitching about others and their perfectly viable, even if not ideal, system.
Quit whining and just say you want to use an alternative system. I suggest you know the names of the system or systems you want to discuss as well.
Seeing as you cannot already even name the system you are crying about I suggest just finding a named system you DO like and directing riot's attention to said system
examples
ELO
Microsoft Trueskill
Glicko 1
Glicko 2 (PDF format but probably something you would be interested in)