It is common over time for dryers to stop heating. If the dryer is electric, this usually means the heating element has burned out. If it's gas, the igniter should be checked. Powdered detergents seem to work better than gels. And, the hotter the water, the cleaner the dishes.
Dishwashers have seals that last much longer if they remain wet and are used regularly.
Use your dishwasher at least once every two weeks - even if that means running it through a short cycle empty. If the dishes aren't getting as clean as they used to, there may not be enough water getting into the machine. It's common for the water inlet valve to need replacing every five to six years. You can even use the feature to preheat the oven for you. Just set the timer to turn on the oven 15 minutes before you'll need it, the oven will be hot and ready to go when you are.