To be honest not really? Metroid Prime fans have always been a vocal minority amplified by the specific demographic of person who was a Nintendo influencer during the Wii U era and the perceived state of the Metroid franchise coming off of Other M and Federation Force.
Metroid is in a much better place than it was 8 years ago. The series has a clearly defined future and a dedicated dev studio (Mercury Steam), and between Samus Returns, Dread and MP4 (along with smaller stuff like Ridley in Smash), most fans I think feel assured that the franchise won't be abandoned. And with Nintendo generally doing more to appeal to adult/western/"mature" fans than they did in the early 2010s, Metroid Prime 4's existence and success have lost the existentialism that defined their announcement. Nothing is riding on MP4 anymore. And that sort of momentum was just never going to hold up for 8 years to begin with. Hype fatigue is very real and people will not maintain that level of excitement for that long. Nintendo's audience has changed pretty significantly in the Switch generation and Metroid Prime just doesn't have the cultural capital it seemed to in 2016-17.