One of the big positives of these types of movies is that they introduce old (often cult) movies and TV shows to a new audience that might not have seen the originals previously, thus lengthening the longevity of the fandom and franchise overall.
Before I start on my thoughts about the remakes and reboots, there is a question we must resolve. What is the difference, if any, between the two? Remaking a movie means that you take the story of the original and remake it for the new audience. One such example is the Ben-Hur movie from 2016. It followed the story of 1959's movie quite closely, but adapted it for the modern audience. A reboot, however, takes the franchise into a completely new direction, most of the time ignoring previous iterations of the media, such as with Batman movies.
One of the big positives of these types of movies is that they introduce old (often cult) movies and TV shows to a new audience that might not have seen the originals previously, thus lengthening the longevity of the fandom and franchise overall. This often means more money for the holder of the original franchise's rights, and more money for everyone involved.
However, remaking and rebooting often creates a sort of disconnect between new fans and old. Producers update aspects of the original movie or franchise that do not really work with the modern audience's values, but not everyone agrees on what worked in the show or movie and what did not. The new Charmed series is a prime example of that. There is a big chasm between the fans of the 1990s classic and fans of the new ones, as some of the key aspects of the show were changed, which angered the fans of the original. Another problem with updating a show to be more inclusive and sensitive is that the historical context in which it was originally made gets lost.
A big problem I have with remakes and reboots, especially with what I call ''inclusion remakes'' is that they take attention and energy away from new projects. Sure, you can have an all-female Ghostbusters or Ocean's Eleven cast, or PoC Charmed, but why remake those shows, when you can make great original stories and be inclusive at the same time?
Overall, while remakes and reboots especially might help renew a passion for a fandom, I think they hurt the entertainment industry more than help, as successful ones are few and far between.