If your instrumental track feels flat even though the composition is solid, here's a likely reason: everything in the arrangement is playing a support role and nothing is actually leading. In a song, the vocal carries the emotion. In an instrumental cue, something has to do that job, strings, brass, a synth lead, whatever fits. Pick one instrument per moment to exaggerate and carry the tension or drama. Try this test: strip the drums out entirely. Does the bed still sell the emotion on its own? If not, that's your sign. Try the drums-out test on your current project and tell us what you find.