A holiday is what you make of it, Paphos has plenty to offer for teenagers.
There is a waterpark, a go Karting track, mini-golf course, bowling, plenty of watersports etc.
There are restaurants and plenty of bars etc. but there are also quieter areas too and many historic sites to visit and great trips which you can do from Paphos.
The beaches are not great but nevertheless they are there and you can swim in the sea. Coral Bay area has two great beaches and there are many more further west.
It all really depends on what you are looking for in a holiday. Clubbers paradise it is not but it will suit most people.
If a large sandy beach is the most important thing in a holiday for you then it is probably not the best choice unless you stay at Coral Bay.
Hope this helps a little
Viv