I certainly understand the sentiment, and I think you're probably right with 1 in 100. (I feel like that's probably what it feels like for me, maybe 1 in 50 that is 100% impossible to win no matter how perfect I played at the worst, but usually I make enough mistakes it's at least possible I could have won.)
I think part of what makes things frustrating is that there tends to be a misconception about what "doing well" in a game entails. My mechanics are terrible. I forget to use zhonyas when I have it, or use it too late/too soon, don't aim skill shots right, can't play assassins to save my life. However, I play objectives decently and so I think bronze is the most fun division ever bc I can beat anything up to about silver 2 pretty consistently and then my champion pool starts to get restricted if I want to win. I feel like it must be what plat/diamond players feel in gold where I struggle, but for them it seems easy. For me the difference is objective control and utility. I can crush a game as Nunu and have very few kills (although with all the assists I guess he does play into high KDA representing skill, but not the same concept I think if you aren't doing damage/getting kills). In large part I can hard carry in lower elo on Nunu jg because if I don't have perfect early dragon control something is wrong, and I can usually control enemy buffs decently and counter gank consistently to keep my lanes alive so the enemy jg has less pressure and gets less gold. 5 dragons and baron wins low elo games almost every time, and it's easy to get that w/ Nunu control because consume means I control dragon, and blood boil means outer and probably inner turrets are easy off small advantages so we just get ward control and take baron or bait an absolute zero channel team fight.
My favorite champ, Heimer is the same way. I played a game recently and the team went like 1-6 to start w/ bot struggling or going even by 15 minutes and mid feeding their opponent. I was 1-0 or 2-0 top lane w/ cs advantage and tower down I think and swapped w/ mid. Instead of fighting the fed mid lane (which I might have done in the past and possibly lost the game for it) I shoved mid lane and went bot where we tower dived w/ my ult getting a shut down and two assists for me then taking drag. I don't look good from a stat line, couple assists, not carrying right? However, it turned around a losing lane, got shut down gold, a tower, and a dragon, plus freed up bot lane to help push mid and force the fed mid laner to fight 2v1 or 3v1 and stopped them from getting any more ahead/farming easy.
I'm not saying you're doing poorly or that you're wrong in terms of some games being unwinnable, and I'm certainly no great player myself. However, in lower elo the variability is greater, but that can often emphasize great play. I'm sure most games that you have a 5 or 6 kda you win easy (if not it's definitely a macro issue), but I'd wager half the ones you don't are ones you have team problems, but the other half are ones you could win if you changed your play. If you want I'll put my money (time) where my mouth is and review a couple games if you can record them on 3rd party like op.gg or something and I can watch them. I may find nothing to add and just apologize and agree w/ you, but I may find things that I can help you focus on to improve your play and it hopefully would be something that would let you win more. Let me know if you'd be interested, if not, no worries.