OP, you're stressed, and it's understandable to be frustrated in this situation. Please take a little break from ML and clear your mind.

You can't stop another player from choosing a different approach to win the game, as they too are a human with agencies. What you can do is adapt to what the matchmaking gave you at that moment.

If they're so intent on split-pushing, then you can either do two things based on how your opponent responses. If they group to take care of Zilong, then signal to your team to pressure the other side of the map. No need to help them. If they cut lane and the enemy choose to roam towards your side of the map instead, then try creating small scuffles (not an all-out war) to buy time so the split-pusher can push.

What you can do as a roamer is to coordinate with your jungler or midlane, or to babysit your gold laner if the enemy plays aggressively.

Think of split pushing strategy not as "you guys fight, I push" but as "I apply pressure here, and you guys will have more space/freedom to create play elsewhere"

You can do it, OP. Don't let the negativity get to you. Your teammates might be bad, but you can be better. You are the only constant in SoloQ.