What to do as sup when you are playing weakside and ur team just forsake botlane

We all been there at least few times, the enemy just hard focuses u and your adc and you basically feel like it's a 2vs5 the enemy adc is getting even more fed and u just sitting under ur tower feeling helpless, moving anywhere forward to lane is instant death even warding the drake is guaranteed death because their jungler is playing hard bot side camp

Now this might sounds as a frustrated rant but i can keep my cool head and understand the cross map plays what i don't understand is what I'm supposed to do as a sup, my adc is farming under turret but I'm being completely useless i might as well be stealing his xp from sharing it, but the moment u are gone they will tower dive him and they will kill him so u must stay there to make sure he doesn't die meanwhile the enemies are making plays ,what do u do in this situations ?