A dishwasher that cleans but leaves dishes damp is telling you something specific. Before you assume the machine is worn out, work through the simple causes in order, and write each result down. The log is what turns a feeling into a decision.
Confirm the pattern
Check whether the damp dishes happen on every load or only on some. Note the load type, the rack position, and whether the plastics were stacked where water could pool. Dishes that come out wet on every run, across different loads, are the pattern worth investigating. Dishes that are wet only on a crowded or deep-bowl load usually point to the load.
Check the rinse aid and the dry setting
Look at the rinse aid level and the dispenser setting. A low or misset dispenser is one of the most common reasons for poor drying, and it costs nothing to check. Confirm that any heated dry or extra dry option is turned on for the cycle you are running, and that the cycle selected matches the load.
Check the water supply
Run the hot tap at the kitchen sink until the water is warm, then start a cycle. Water that reaches the machine cool can weaken the rinse and the drying. Note what you find, and check whether the problem changes when the hot water is already running at the sink.
Look at the filter and the drain
Clean the filter according to the manufacturer's instructions, then check the sump area for standing water or debris. A slow drain can leave water sitting in the tub, which carries over into the drying stage. Note any change in the drain sound or the time a cycle takes.
Decide what the log says
After a few weeks of notes, you will know whether the problem followed the load, the rinse aid, the water temperature, or the machine itself. If the drying stays poor after the simple checks, bring the log to the technician. The record tells them where to look, and it shortens the visit.
For the typical life of the machine and how to plan around its age, see the dishwasher page.