"Spinoff" much like "reshoots" and "reboot" has become a negative term within film fan circles, often taken to mean a franchise that has run out of ideas and wants to make a quick bit of cash by banking on one of its most popular characters.
And to be fair to everyone who sees a headline about an upcoming spinoff and emits a sad groan, there are a shockingly low amount of them that have actually managed to match or exceed the quality of the main entries in the series.
And even worse, most are just bad movies, full stop. The Nun, Minions, Men In Black: International, Annabelle, Elektra, The Scorpion King, Evan Almighty, X-Men Origins: Wolverine... clearly, crafting a brilliant spinoff is no easy task, so on the rare occasions when these efforts actually prove successful, they deserve to be given a huge amount of credit for - seemingly - doing the impossible.
So while it's true that most spinoffs are bad, a few genuinely great ones do exist, and a select few are even better than the films that they were based on.