I think you can change styles and continue delivering but that's not what In Flames have done IMO. A lot of people give Metallica shit for their decline, but in my opinion albums like Load and ReLoad look like modern masterpieces in comparison to A Sense of Purpose or Sounds of a Playground Fading.
Yeah they have changed styles and whether or not you like the new direction is obviously 100% subjective. I'm not even a big fan of melodic death metal, but I think that's a genre where In Flames really shined when they put out some really strong albums and were one of the pioneers of the genre. Now they have changed into something different, which in my opinion would be a more radio metal sound, and whether or not you like their new sound, I think it's safe to say that they used to be a very influential band that inspired many other bands to make the same kind of music, but it's not like they're relevant at all these days. Again, quality of the music aside, their status has changed. It's kinda similar to how bands like Trivium or KoRn were very hot during a time of their career, but they didn't hit that final homerun and they kinda faded away.