Was this document inspired writing and included in the canon?
No it is not canonical, but it is remarkable for containing the first usage of the word “catholic”. As anyone can see from it, it did not describe any kind of universal community of every believer, quite the opposite. When someone repeats the words of the Creed, “I believe in One Holy Catholic and Apostolic Church” it is the Catholic Church headed up in Rome that he is talking about. Or he has been lied to.