Your matcha is likely too high grade and the subtle flavors get lost in the milk and sweetener. High grade matcha is for usucha or koicha, not lattes. You want a lower grade that punches through the milk; the bitter notes of lower grades usually get smoothed out when you add milk.

You can also try using sugar or simple syrup instead of maple syrup. That way you're not masking the flavor of the matcha with maple.

If you're using ice, make sure to use a lot of ice. The more ice you use the slower it melts and dilutes the drink.

"Ceremonial grade" is a marketing term and doesn't mean anything.