The question is rarely whether a phone is good enough, since a recent phone resolves far more detail than most product listings ever display. The useful question is which controls you give up, and whether your products and your volume actually need them. Judge the tool by the job.
Where phones do well
For matte products in good light, a modern phone in its highest-quality mode produces files that hold up at listing sizes. Computational processing handles noise and dynamic range automatically, and the small sensor gives deep depth of field, so an entire small product stays sharp.
Where a camera earns its place
A dedicated camera gives you manual control over aperture, shutter and white balance, a mount for lighting triggers, raw files with more editing latitude, and interchangeable lenses. It matters most for reflective goods, large catalogs shot to one specification, and anything needing shallow focus.
Settings that matter on either
Shoot in the highest-quality format available, raw or the phone equivalent. Lock white balance rather than letting it drift between frames, turn off beautifying and scene-detection modes, set the lowest practical ISO, and disable the flash. Consistency between frames matters more than peak quality.
Action Step
Photograph one product with your phone and, if available, a camera, using the same light and position. Lock white balance and use the highest-quality file format on each. Open both at full size, compare edge sharpness and color, and write down which you will use for listings.
This lesson is educational and reflects general practice. Results depend on your situation, market and effort; adapt what you learn to your own context.