It happens to you, and it happens to them is also a fact and though statistics can be little mind numbing it is a more accurate description of the entire situation instead of ignoring when the other guys feed as not being a problem and it's only about when our guys feed. Pathetic describes a thing "arousing pity, especially through vulnerability or sadness", or to be "miserably inadequate."... Adjusting one's play style to accommodate the observed cause/effects and their results might be an option one has not considered, or efficiently spent energy on.
It's easy to come back from so many loss's that it's actually more frustrating than the loss itself when the team gives up and throws what was otherwise a perfectly winnable situation in this speakers experience. For instancee, the amount of times our team has come back after I've had to play guidance councillor as a Sona support in silver elo god help me what trying times they were. With ridiculous deficits early game becoming a winning game by just scaling up, often just me finishing an Ardent Censer (sometimes two or items so e.g + and Athenes) and suddenly destroying team fights... Silver is a strange place dominated by irrational and emotional people one must do one's utmost to keep in check is all I can conclude... I'm assuming we're talking about Silver and/or Bronze here (I haven't played bronze so I can only assume it's has similar struggles) as it does happen in Gold, but Gold players have in general from what I can tell learnt the most important aspect of what not to do to regarding feeding which the players in Silver by comparison have not yet come to terms with and no it is not "don't feed". If one has not yet noticed yet life is full of crazy paradox all upside down back to front or just straight up side-ways tangents then here's a heads up, it is. I've played WoW arena to 2.2K as a priest and a rogue so this whole gaming thing is not new to me and how macro/meta is viewed though differing tiers and how each understands concepts such as balance and "what is efficient game-play?" substantially differently. I'm learning LoL so I have much to learn quite obviously or I'd already be somewhere higher than Gold... In LoL I've so far found that in Gold, the players have a reasonably firm grasp of the concept that in-game application of emotionally charged adjectives such as "pathetic", when used in combination with personal pronouns will cause far more loss's than will feeding team mates. Not to mention unnecessary mental anguish for all involved and will regardless of win/loss also get in the way of learning whether it's expressed inside or outside of the game... In short it's just not an intelligent idea to forget how fortunate one's position is in life to have the option/time to play a computer game, but lets address the concern raised by the OP as best I can regarding Leagues balance and leave philosophical considerations for Captain Obvious.
Play scaling champions --- Games go for ages and unless a game is closed in a timely fashion (more often than not it won't be in low elo). That early deficit won't be nearly as significant once you have scaled with time/items and if you are a late game champ you can still easily carry regardless.
Play champions that excel at "Arams in Mid" --- Games will go for ages, and so often will be decided by team-fights & death timers rather than intelligent macro play in silver and I'm assuming Bronze also. Be the deciding factor by playing champs who are strong in teamfights, or know how to carry through macro since there's a good chance no one else will know how to actually do it. In silver, people generally know strong macro play exists but what it actually is not so much.
**Learn what good macro play is ** ---- The rest of your team will often be too busy with the Aram in midlane so shove those side-lanes yourself, pay attention to the map and ping intelligent macro decisions/shotcalls. If macro play is a new concept then play some google and learn what sound macro play means, and when you are the one carrying make sure you know how to turn it into a win instead of simply further increasing one's KDA... Only type in chat if it's necessary, such as when sometimes one may be required to gently remind one's team mates what the win conditions of each team are and how playing to your own teams strength as opposed to the other teams is surely sound logic. You'd be surprised how intelligent humans beings are when one communicates in an intelligent fashion.
Don't give up --- The opposition is likely to make a mistake that can captalised on, but one's team must still be on the field of play when the mistake occurs in order to do so and so never give up and begin int'ing. Do not not be there purely because of irrational emotional reasons either, and don't encourage one's team mates to not be there either with emotionally loaded adjectives. We need our team mates so always act gently, and use mute when kindness fails.
As an example, this speaker got sick of all the nonsense in Silver, got sick of winning bot-lane and waiting patiently for statistics and all his fed ADC's who did not know how to carry, got sick of winning games being thrown by one late game team fight negating all the hard work it took to get there ...(happens both ways and is a massive win condition all of it's own in low elo games and no one seems to give it the significance it deserves regarding hard carrying and not giving that one guy the chance to do it if he happens to be on your team because by god no one can stop him no matter how hard and often they win their lane)... And so he then decided that since he wasn't going to play a lane he was was going to play AP Janna and due to suddenly being able to hard carry as well as having an idea of good macro and learning some more through additionally being the carry as opposed to only carrying the carry as he was before, in no time flat the speaker streaked into Gold division where he can thankfully play with people who don't make the game unpleasant with emotional and irrational behavior (so far that is one's experience). It's a game, if it's not fun then don't play. If not winning is not fun then work out why one is not winning. Listening to people who are winning is a place to start if one is out of ideas.
