If they are camped - not ganked once in awhile, but actually camped, I understand them doing poorly. In all other scenarios, a losing botlane as TWO people to protect each other. They have TWO people to ward for ganks (one of which usually builds sightstone) so they should have perma vision of incoming ganks. They have range to make it safer to farm and harder to gank. They have defensive summoner spell(s) in exhaust (sometimes) and heal/barrier (pretty much always). There is no reason for them do die repeatedly when they are largely left 2v2.
I regularly get games where a bot lane has far worse kda 2v2 all laning phase than I have while being camped 2v1 top. This should never happen. Low elo botlane is on average the worst/least intelligent lane. Not saying there aren't some really smart and good botlaners, but on average, they feed the most compared to how much they get pressured. If they played appropriately, a winning mid and top early more than compensates for a bot that is behind. Moreover, the winning top and mid can then take their lead, win teamfights early/mid game off THEIR lead, and get their botlane right back into the game - provided bot played well and didn't int just because they were behind.