It's hard to overstate the importance of 2008's Iron Man. The film didn't just launch the Marvel Cinematic Universe; it also established so much of what would make the MCU successful. In terms of style, tone, and even specific character arcs, Iron Man established a pattern that Marvel has largely adhered to over the course of the last decade. That's not a criticism. The reality is, Marvel Studios are very good at taking aspects of that formula, and subtly reworking them to create something fresh, new, and original.
But Black Panther changes all that. While it uses all the familiar tropes, the film twists them in unexpected and transformative ways. Both in terms of plot, and in terms of overall approach, there's no going back after Black Panther. The MCU simply cannot stay the same.