Most dishwashers don't drain completely and it's normal for the dishwasher to have a few inches or so of standing water in the dishwasher.
So if you notice a few inches of water left in the bottom of the dishwasher it doesn't mean anything is wrong with the dishwasher.
My dishwasher leaves a few inches of water in the bottom of the dishwasher and I asked a service tech about it and he said that it was normal.
Now if the dishwasher leaves too much water in it then the pump could be going bad or you have a partially clogged drain in the dishwasher.
But having an inch or two of standing water in the dishwasher is normal.