It wasn’t just the quote that gives a nod to Kirby. The Fantastic Four of the MCU are from a different, retro-futurist Earth ...

The film shows Kirby’s birthdate immediately after the quote. The tribute remains outside the film’s narrative. No characters mention Earth-828 or refer to its numbering in dialogue.

On the one hand, Kirby's quote at the end of The Fantastic Four: First Steps is fairly self-explanatory. It's him reflecting that art will always say something about its creator and their values.