The hull is unlikely to be the problem.
It sounds like it is light winds that are the problem.
So my tips are;
Most people that are slow in light winds are because they think they are. Consequently they stop concentrating and then say I told you so.
Focus on what the boat does and not what others do. The first place to look is nose transom out maybe a little heel and T-foil a little positive to adjust for pitch.
Sails and need to be open and a little flatter than you would think.
and above all practice