Tor provides anonymity by building circuits with three relays. So instead of connecting directly to the destination server, a connection is made between each relay of the circuit and this takes more time.
The Tor relays are run by volunteers in a decentralized way. So all relays are not of the same quality. Some are big and fast, while some others are smaller and slower. As a whole, the network could be faster if it had more capacity. To improve the capacity of the Tor network, you can either run a Tor relay yourself or [help existing relays](https://www.torservers.net/partners.html).
