I love exploring lesser touristed sites so I say go for it if that matches your travel style. Of course traditionally touristed places like Siracusa, Noto, Catania, etc are lovely worthy destinations but youcan always plan to come back and explore those areas someday. I am going to throw out some suggestions that you can research on your own. Of course, as many have mentioned, many smaller towns will be very quiet, with their townspeople going about their everyday lives. But you know that up front. I assume you will have a car otherwise many of these places will not have lots of public transport options.
West of Palermo- 1) Borgo Parrini (very colourfully decorated small village). The decorations, sculptures and Artworks have been added lately to bring new life and interest in this old village. I was there in March, and there were no tourists and little open but it is pretty and photogenic on a sunny day. Combine it with a visit to Segesta or Erice or Castellammare del Golfo.
Southwest of Palermo - 1) Mazara del Vallo - This seaside fishing town has a very compact historical center, filled with Tunisian influence. Pretty mosaic and tile murals on the walls of the narrow alleyways that depict the culture and history of the area. An old Casbah area with a small museum that houses the Dancing Satyr, a beautiful ancient Greek bronze statue that was pulled up in the nets of local fishermen in 1998. I liked this town very much.
2) The archaeological park at Selinunte - Not far from Mazara del Vallo. The seaside park is huge and houses the ruins of an ancient Greek city. Beautiful temples, no crowds.
3) Sciacca - nearby fishing town/city known for its pottery and seafood.
4) Old and New Gibellina - Old Gibellina (Cretto di Burri) is one of the eeriest places you may ever visit. The small rural mountain village was completely destroyed by an earthquake in 1968. The ruins were left abandoned until 1985 when Italian artist Alberto Burri began a project to encase all the ruins in concrete. The project was completed in 2015. It looks like one big concrete maze in the middle of the open countryside. Extremely unusual and unexpected. The government built a new Gibellina town about 11 kilometers from the original site. That town has many outdoor sculptures and is considered an outdoor museum. If you go there you must stop in at the Museo delle Trame Mediterranee. Don't miss the huge outdoor sculpture titled Montagna di Sale- Mimmo Paladino. Very, very unusual.
East of Palermo more or less on the route you are considering -
1) Tindari - If you like churches there is a pretty sanctuary dedicated to the Madonna of Tindari, a dark wooden statue of Mary pulled from the sea. The church sits high on a cliff with beautiful sea and beach views. Within walking distance of the church is an archaeological site with a Greek theater. The nearest towns are seaside Oliveri and Patti. Oliveri is very small. I stayed overnight there once in late September and it was pretty empty. Recommend as a stop if you like religious sites but not a stayover spot.
Near Etna
Zafferana Etnea - I have not been here yet but it has been recommended to me and is on my wish list.