A denture picks up plaque the same way teeth do, and because it is not living tissue it does nothing to clean itself. Left alone it builds up film, stains, and smell, and the tissue underneath gets red and sore. The version I see most often is a yeast infection under the plate: uncomfortable, easy to miss because it is hidden, and almost entirely preventable.
If you still have some of your own teeth, it matters more, not less. A partial denture sits against those teeth and will hand plaque straight to them, so a dirty partial turns into a decay problem in the teeth you are trying to keep.
Cleaning it is not complicated. Brush it every day with a denture brush and something non-abrasive. Not regular toothpaste, which is gritty enough to scratch the surface, and those scratches give plaque more to hold onto. Rinse it after meals when you can, and leave it in water overnight so it does not dry out and change shape.