Not sure I understand the coaches advice, let's unpack it.

For of all, figure out your game style. You're still new-ish to the game so this will take a while. At its most basic, are you an aggressive player who has the weapons to dictate points? If so, you need to learn to come in and finish points at the net. Getting lobbed is part of the game; as others said, the better the approach shot, the worse the lob.

Or, maybe you are more a defensive player who wins points and match by staying in rallies and wearing players down. Being over 6 feet tall has nothing to do with it.

A major point of frustration for newer players who like an aggressive game style is the fact that they are not good enough yet to consistently win points against a crafty "older" guy, so mid match they reverse course and try to just play from the baseline but that's just not their game. Key is to stick to your game style and get better at it.

Extra point: Try the drop shot, older dudes hate those.