Have you checked the exhaust hose? It might be pinched and not allowing the air out.
Just remember, if no one knows you’ve worn the clothes, they don’t need to be washed in the first place.
Most likely might be the heating element, or the exhaust duct has an obstruction of lint or something. Since we know the screen trap is clear, that's out. But sometimes, and not often, in the trap area pending the model/design, lint cakes up around the intake duct. And I assume your dryer is spinning, but this too has been the case sometimes, it not spinning that is. I guess we'd be surprised, but some people don't pay attention to that sort of stuff. I'd think you'd really have to try and not pay attention to not hearing the motion inside, but everyone is different and not all pay attention to such things.
Source: I uninstall/install washers and dryers, also drop them off to people that know what the fuck they are doing. Heard some possible problems they have fixed over the length of some time now. Not a pro by any means, just heard some stuff.
Of course if you cleaned the lint trap once in a while it would be much better.
My dryer worked fine in my previous apartment, but when I moved to my current one in January last year, the top would overheat and the clothes wouldn't dry and stayed humid even after spending considerable time in the dryer. The issue ended up being that the previous tenants never bothered putting on their lint filter on their dryer, so all the lint that would normally be trapped by the filter ended up clogging up the exhaust duct inside the walls of the building. The building's caretaker used a commercial vacuum cleaner (with rags bunched up around the vacuum hose) to pull all the lint out -- I had the equivalent of a small kitten in there. Dryer has been working like a charm ever since. Perhaps your issue is something similar to this.
Holy Fuck! In many years of redditing, this is the very first time I have ever seen something advertised as a flowchart AND IT ACTUALLY IS ONE!
They missed out one house-fire-preventiung step though: "remove lint from lint filter".
It could also be a bad thermostat or high temperature cutoff switch. I replaced my htcs and gas flow silinoid (sp?) for about $40 iirc. You can find a parts diagram online at any good appliance parts website.