The word Gospel is from an old English phrase meaning Good News.
The Great Commission refers to the final instructions JESUS gave to His disciples. It was the final assignment He gave to His students, His followers to go preach the Gospel, the Good News. This assignment is to go preach this Good News message of the Gospel everywhere. All disciples of JESUS of all times are in this way commissioned, instructed, assigned and sent out to continue sharing this message, to make more disciples, more students. All disciples are to make more disciples and always to teach those disciples to observe and do everything JESUS instructed His original disciples. That everything also includes this final instruction which ensures that this message will always continue spreading and always leading to more disciples.
JESUS is the Great Shepherd and LORD, and He is the Leader of all His people and all who call Him LORD are to follow Him as LORD of all.
All who claim to follow Christ are responsible for actually carrying out the Great Commission.
Only those who are active in obeying JESUS in all things including His Great Commission are truly His faithful disciples and students. Those who are not active in obeying His clear instructions are not truly faithful disciples and cannot really be called Christians or "like Christ" in the truest sense of the phrase. The spread of the Gospel is hindered by all who consider themselves Christians yet who are not active in spreading this Good News. On the Day of Judgment, all who claimed to follow JESUS and do His will, but who did not actually obey and do as He taught will be sent away from Him as workers of iniquity.