If Boba Fett hadn't undergone any significant changes, then his story would have no point. He went through a terrible experience when he fell into the sarlacc pit in Return of the Jedi ...
"The Book of Boba Fett" episode one explains that Boba escaped the monstrous Sarlacc pit due to his Beskar armor keeping him from being crushed or melting inside the Sarlacc's stomach acid.
Over the course of "Star Wars," "The Empire Strikes Back," and "Return of the Jedi," the masked character of Boba Fett only has four ... a Shai Hulud on Arrakis a Sarlacc on Tattooine.
The finale of The Book of Boba Fett did what no one expected: It actually featured Boba Fett. You'd think that would go without saying, but it was looking dicey after the two previous episodes.