A number of things can cause this.
The overall problem is slow updates. This can be caused by the client computer, or the Internet connection, or both. If your computer is resource starved it is going to be slow about adding new resources such as a new item that has come into view. This same issue can incorrectly point to a potential issue with the Internet connection.
However, the Internet connection can also come into play. If the upload rate is such that the data simply cannot be sent fast enough (for whatever reason, and there can be many), then things will simpy slowly appear.
The server can be a factor, but it would effect everyone equally.