For an electric clothes dryer that's taking too long to dry clothes it's usually caused by lint being clogged up in the vents or where the lint catches.
But if your electric dryer is not heating up at all to dry the clothes then most likely your electric heating element for the dryer has went out.
Whether or not it's worth repairing will depend on the age of the dryer.
If the dryer is only a few years old and everything else is working on the dryer then you can likely get the heating element replaced for $100.00 with the part costing $50.00 and the labor another $50.00 or so depending on the appliance repair shop.
If the dryer is 8 years old or older then it's not worth repairing the heating element since most likely something else can and will go wrong with the dryer soon after heating element replacement.