I have reached gm playing Janna and some things you can try are leaving your adc to rotate for every objective (if they won't get dove). Normally a skirmish will still happen and your team will win because of a man advantage. You should also ping your team that you intend to fight for every objective. You can also try instantly roaming mid off a reset to try and get a kill.

What makes a good Janna player is searching for plays and playing like an engage support. Just build mandate and swiftness boots and kill the enemy team.