You have the payoff but too few ways to activate it.
Look for Intrepid Rabbit.
Rabbit and its offspring give Mentor ground targets for counters. Later flying creatures keep adding counters to those targets.
Your synergy is already working but you keep falling behind.
Take an early play or answer before another expensive reward.
An all-flying board leaves Mentor without a legal counter target. Include ground creatures that still matter when drawn late.
The support is missing
Favor castable creatures and interaction if narrow support does not arrive.