I have a 98 Sunrise, one 4.5hp jet pump and one circ pump.

The jet power in general seems rather weak. I tried playing with the motor connections, checked all the jets/diverter valves, etc.

Are these just inherently not very powerful motors?

4.5 hp is pretty robust (in reality its probably a 2hp motor with 4.5 starting hp) but the action really depends on how many jets you have open. One pump for a bunch of jets and none of them will have much pressure. You also may have wear in the pump and its seals which would decrease its effectiveness. In a 11 year old pump that should be expected.