The three main disadvantages of Telnet are that it is insecure, it is text-based and working on a computer through Telnet is slow. That being said, Telnet is still considered one of the best ways to remotely log into a computer and access applications and files, according to BBC.
Due to the fact that Telnet is text-based, users are limited in the type of programs that they are able to use on the machine they are accessing remotely. This is because Telnet is not able to open any graphical displays on the client.
The reason why Telnet appears to run so slow is the fact that everything that is being typed by the user is being sent over a network to a server. After the information is sent, the computer has to act on it and send the information back to the user. The slowness of Telnet is amplified if the user is using a slow Internet connection, such as dial-up.
Despite the pitfalls of Telnet, this protocol still has its uses. For example, it is possible to connect with Telnet to a POP3 email server. This makes it possible for users to read email messages and delete spam or huge emails before ever having to download them to an email client. It is even possible to surf the web using a Telnet connection, but this only allows the user to surf the web in a text-based format.