Spider-Man: Homecoming may be the first movie in the MCU with Spider-Man but in reality, it was the sixth film starring the character within a fifteen year period, the second reboot of the franchise, and it starred the third actor to portray Peter Parker. While I'm sure everyone involved in the MCU would have loved to have been the first to bring Spider-Man to the screen, the reality is they weren't. The classic iconography of Spider-Man had already been established. And been done so very well. Two times over, in fact.
Retreading anything that had been in the Raimi or Webb films would have been an enormous waste of time, not just creatively, but on a commercial level as well.
On top of that, the MCU was deep into its own continuity by the time their arrangement with Sony allowed Spidey to enter that world. So characters were well established and larger storylines were already in play. Bringing Spider-Man into that world at that point meany that there was going to be changes from the continuity of the comics. Peter had to be woven into an existing, complex continuity rather than be part of it from the start.
And on a third point, while Black Panther is always guaranteed to be a part of the MCU, Spider-Man isn't. While the deal with Sony seems very amicable and mutually beneficial, there's no absolute guarantee it will last forever so it would be a mistake to not take full advantage of Spider-Man's inclusion in this larger universe while the deal is in place. And it wouldn't just be a mistake creatively, because a literal whole new world has opened up for the character on screen for the first time ever, it would be a mistake on a business level. Sony isn't going to agree to let Marvel bring Spider-Man into their cinematic universe only to have Marvel keep Spider-Man isolated in his own corner. If that's what these movies were going to be under Marvel, Sony would have just kept the character under their own umbrella. Sharing Spider-Man with Marvel means putting Spider-Man squarely in the MCU, whether it be through having Tony in Homecoming, Nick Fury in Far From Home, or whatever other MCU character is featured in the next film.
So, the reality behind the Black Panther movies and the MCU Spider-Man films are very different.