The force pump represented a significant advancement in technology.
At about the same time, he pushed a bucket upside-down into water and when he pulled the bucket out, he noticed that it wasn't completely wet inside. Those two events got Ctesibius to thinking about air pressure and water pressure. The bit about air pressure is significant because up until then, people basically viewed air as nothingness. They understood wind but didn't see air itself as a real thing. So considering when it was invented - before much was understood about hydraulics, Ctesibius' force pump was quite complex and represented a major advancement in water delivery.