What do you do when you cant contest objectives, 5v5, or pick off the enemies?

/ff

Joking what I do personally is defend inhib towers at all costs, drag the game out until there gold lead no longer matters

Do you have a reliable split-pusher with an escape OR a strong 4v4/4v3? Yes: split-push. No: go to the waveclear question. Do you have waveclear? Yes: wave clear and stall out. No: clear vision and establish a defensive pick.

If you don't have a split-pusher, wave clear, or way to pick (and your teamfight is inferior), then you're kinda boned. They'll just push advantages if they're good and either bleed you out or dive.

Push lanes

If the enemy is better than you at 5v5ing and getting objectives, and you are physically unable to out-rotate them to get a pick, you're in an extremely terrible position and have next to no chance of winning. Just try to group mid and bait them into starting a 4v5 or 3v4 that they cannot win. That is literally your only chance of getting even anywhere near back in the game.