Here is an article talking about how Agents of SHIELD went from one of the biggest things on television in 2013 to a struggling show in 2018.
https://tv.avclub.com/how-did-marvel...ult-1826058082
Yes, the show is still on, but that is mostly due to Disney's influence. If it were any other show that had the same ratings, it would have off the air after season two. This show may be an underdog, but it is a very lucky one.