Fluff and reshape before judging.
A folded towel underneath can reveal what is missing.
If it collapses quickly every night, structure may be gone.
Redistribute the fill
Many soft pillows need regular shaking and reshaping. If the fill moves to the edges, the center can collapse. Fluff it from multiple sides and smooth the case so the pillow does not start the night uneven.
Add temporary height
Place a folded towel under the pillow for one or two nights as a test. If the pillow suddenly feels better, the problem may be height more than softness. That tells you what to look for if you eventually replace it.
Use a supportive case setup
A very loose pillowcase can let a soft pillow spread too much. A well-fitted case may help the pillow hold shape. Avoid making the case so tight that it creates lumps.
Know when it is done
If the pillow no longer holds shape, flattens quickly after fluffing, or needs constant adjustment, replacement may make sense. Choose based on the problem you identified: more height, firmer edges, better fill stability, or a cooler cover feel.