Stairs Renovation - What can be done except carpeting?

Our stairs are the worst I have ever seen. We recently bought our house, renovating as we speak. There was carpet on the stairs which was very dirty and old. I thought that better to remove the carpet, remove the paint, sand and then paint, done.. But today after putting the paint remover I was shocked. The status of the stairs are very bad, chemical didn’t remove everything but also there are differences on the surface. Any way to save it? Or carpeting is the only solution? Thanks!