According to this article the problem seems mainly two fold, conductivity and thermal inertia (among other factors).
During washing temperatures get relatively hot (depending on the particular program chosen) to promote sterilization and help with cleaning.
Conductivity: Different utensils are made of different materials which will absorb this heat at different rates. Plastic has relatively low conductivity compared to say a metal pan or stainless steel object, thus both gaining heat slower and transferring that energy to water less efficiently leading to less evaporation.
Thermal Inertia: Plastic objects are generally thinner and lighter, plastic is generally also less dense than other common kitchen materials, leading to retaining less heat, and conserving less energy, thus remaining warm for shorter periods, again promoting less evaporation.
There may also be other factors at work; such as surface properties of plastics like roughness and porosity that make it hydrophobic, which may cause water droplets stick more to its surface, or evaporate slower.
Briefly open the door
I have recently developed a practice that I feel helps getting most items (even plastics) almost dry.
After the cycles finishes, (the sooner the better so that the least amount of heat is lost), immediately turn off the dish washer and open the door.
Leave it open for a few brief seconds, long enough to let most vapor escape, but short enough that the minimum amount of heat is lost.
After that close the door again and let it sit for a while, no need to shut it tight, leaving it ajar will suffice. Ten to twenty minutes is probably more than enough if you are in a hurry.
This will ensure a lot of the humidity will leave the compartment while still remaining warm, promoting quicker evaporation, ensuring that most items will be either almost dry or have a minimum amount of water when you return to unload the dishwasher.
Shake Plastic Items
One other optional thing you may do in addition to the previous procedure, (if you can waste the time and have the energy) is, after opening the door while waiting for the steam to escape, individually grab any plastic objects and one by one give them a vigorous shake to loosen any droplets on its surface.
If your ratio of plastics to other materials is anything like mine those should be a minority so it shouldn't take too long. One or two shakes per item is generally enough, just let them splash into the sink, or even back into the dishwasher to get most of the surface water off. Then just put them back in and close the door again and let them dry along with other items, the remaining heat should take care of most residual humidity.
As mentioned in the comments, if you have no delicate items that might break, you can also just give the whole rack a shake instead. Items with intricate designs or crevices that pool water may still benefit from a good individual shake though.
Use Rinse Aid
In case you aren't already for some reason, using rinse aid seems to helps considerably achieving drier items after the cycle.
Backstory: After purchasing a new "fancy" zeolitihc dish washer we were told it needed no rinse aid since local water quality is satisfactory; so we didn't for a while, and were pleased with the results. In time however we found, that despite all the bells and whistles the new dishwasher seemed to achieved poorer results compared with the previous one.
So for a change we decided to add some rinse aid once and it made a very considerable difference in the wetness of all item types after a cycle, not only plastics but also, metals, glass and ceramics (in addition to considerably reducing cycle duration by 1/3 of the time, thus also saving energy).