If your top laner (Jax, Trundle, etc.) is split-pushing, DON'T FUCKING START A FIGHT
Why is this such a hard concept to grasp?
When your top laner is out there solo-pushing a wave, your job is to group up with 3 of your other teammates & pressure the enemy team in other lanes that's not where your top laner was split-pushing. From there, all you have to do is try not get caught off or even start anything at all. Just lay off the battleground, keep the enemy teams' eyes on you while making them forget the splitting Jax pushing through the inhib. Only if you notice the enemy team attempting to back to push the split-pusher off, that's the time for you to stop them from backing at any cost. Or unless if it's an emergency where the enemy team decided to hard-engage on you, that will most likely be the time for the Jax to TP in for assistance, which is fine.
To conclude, stop thinking you can 4v5 the enemy team whenever you lay your first sight on them. Especially Yasuo mains...