Letter Writing has truly become obsolete.
Obsolete:no longer in use or no longer useful
In this day and age, technical communication is much more prevalent among the world than "snail mail". Therefore, more messages are being sent via technology which makes getting your message to the recipient much more difficult. To make my point I will use an example. If one was to try to communicate with Matthew Santoro(https://www.youtube.com...) via twitter, it would be lost in the sea of other tweets sent to him. However, if one was to send a letter to Matthew Santoro, he is more likely to read it as it stands out. Infact, he has a segment in which he reads and responds to every letter and package sent to him (https://www.youtube.com...) . If one was to send him a letter, it would have been read and responded to while a tweet would not have. He seldom responds on his twitter page(https://twitter.com...).
Letters are not obsolete as they have at least one current use.
Conveniecne is the key
What you say is true. However, most people are not writing to popular youtubers on a daily basis. Further, maybe instead of a tweet, someone could easily send a text. The example you used does not apply to the average person. True, writing a letter to someone does really stand out. However, most people need a reply as soon as possible. People in the 21st century are looking for convenience, and "snail mail" does not meet the standards. People find texting to be easily done.
Just because something stands out does not mean it is still present in today's society.
You're now arguing that technical communications are more efficient for communication than letters. I urge you to look at the title YOU chose for this debate. You chose the words "truly" "obsolete". I then argued that there is at least one use for it, therefore disproving the statement "Letter Writing has truly become obsolete." Please don't disregard this as semantics. Truly obsolete and inefficient are different. I believed both you and I were debating obsoleteness which is why I wrote the arguments I did.
"However, most people are not writing to popular youtubers on a daily basis."