What you playind and which lane? If you are mid, your team has a carry or more, you down the tower after 9min and then the laning phase is over, then it's your fault you loose the game.

I play almost always with Sivir, mostly in mid or solo lane. And i seriously try to NOT take the tower down, because i have seen things go bad after i do that. (feeding on both ghosts camps and the wolves while defending the own tower is ridiculously easy with Sivir btw...)

About the topic, if you see that the matchmaking is broken, please try to be constructive. Like what riot could do to identify bad teams.

Example:
If it was a fact that a team needs a tank to win, riot could calculate the chance for people to choose a tank based on their last 20 matches. And then try to even this chance out for both teams.

OP, if you are two wins from lvl30, can I suggest you to do 2 custom games against bots?

Matchmaking has to improve A LOT before we can say it is horrible.Currently, it's far beyond horrible. And yet Riot keeps braging about how good it is and won't even let us host our own rooms so we can decide who we play with, instead of a (beyond) horrible MatchMaking.
I hope they fix it Soon(TM).

I find players who call others "noobs" and throw a fit early game then whine to try to get their team to surrender at 25 to be a bigger problem than most early game mistakes.

I've had several 40min comebacks after my team whiner started a surrender at 25mins... if we could get the whiner not to AFK.

Otherwise, if you're having repeat crummy games you might want to evaluate the common denominator - you.

Although it's not always the common denominator that's at fault..I've been in plenty of games with level 30's and excelled because they were intelligent and we actually worked together. However...I've also gotten plenty of matches with people level 5-20 (Yes a 5 and a 20 in the same match together) where everybody just does whatever they want, runs into enemies alone constantly and feeds the enemies from level 1 on. I find that I get more of the latter group than anything else and I suspect much of it is on purpose.
It's just really tiring to know that in a match with smart people you do well while if you queue alone you have a 90% fail rate because a lot of people just can't work as a team.

I think what Riot should do is filter posters better. You see how this guy just ranted and people left comments and he hasn't even returned. Imagine if Riot had actually been like wow, we never realized this, let's have a good discussion with this guy. The guy didn't even have the curteousy to come back and reply to the replies. Guys like this seriously just have one thing in mind, themselves.

He probably plays Tryndamere and wonders why his team dies when he endless rages and swishes away over a wall.

Most likely..although if I play something like Master Yi, I run away when 1-2 squishies from my team stupidly rush into the entire enemy team gathered in one spot..but that's just because a third squishy isn't going to do much of anything except die. And the teams generally speaking are unbalanced. I've usually get matched with people anywhere from level 7 up to level 30 (me being level 21). In the long run, the lower levels tend to feed more and the higher levels (at least in the games I've gotten) are bossy or don't speak english.