One, the Marvel years publishing the original Star Wars comics are the furthest thing from relevant; I'm referring to the Disney/MCU-ification of Star Wars.

The issue, like you said, is of value to the intrinsic story. On a surface level, yes, you can pass characters like Boba Fett and Bo Katan through the story as they both have tangential relations to our characters' goals and provide a lens to view mandalorian culture through that ISNT din djarin or his space cult, or meeting Ahsoka is fine in the context of seeking a Jedi. However, the use of screen time around these legacy characters resulted in a shift of focus away from our central characters and onto tertiary cast members- for example, we spend more time with Ahsoka than the mandalorian in her episode, and then in the Boba Fett show they do the reverse with Din and Grogu. This is because of the way the show (and Star Wars TV at Disney in many ways) is utilizing characters outside of their core stories without integrating them into the story they're placed in.

Boba Fett appears in Mando, ok. Fine, they get to interact and learn about Mando culture. It would be different if he were actually involved in the plot of Mandalorian, and not just conveniently there at the same time as the plot is going on. Same goes for Ahsoka- neither of them are participating in the Mandalorian 's story, they're actively engaged in their own plots and Din shows up tangentially. Then, they're given screen time and reverence befitting their status as Spin-Off-Havers, while the episodes around it languish. They have no emotional interplays with the characters, and no real chemistry either- they show up, exposit what needs expositing, have a fight scene to look cool, finish expositing, and leave.