I didn't mind 02, the last few episodes were like PLOT TWIST AND HERES ANOTHER PLOT TWIST but other than that I didn't mind it because it gave some sort of post story for the original digidestined and what they are doing after the whole adventure though I didn't like how Sora ended up liking Matt because what about Tai yeah it showed he had developed as a character the way he took it but... Tai and Sora were supposed to... Plus I like Veemon and the digimon movie for it where they meet willis made me cry as a kid.
Then you have the ending that was, for the most part, really out of the blue and almost ridiculous. Yamato/Matt suddenly becoming an astronaut, Sora/Matt although we saw little development on screen
There was someone on Tumblr who asked Hiroyuki Kakudou, Digimon creator and series director about Yamato and Sora, especially their relationship and occupations in the epilogue.
Yamato became an astronaut for several reasons. From a franchise standpoint, 02 was going to have its own sequel, where enemies came from space. Yamato become an astronaut is a remnant of this idea. His official Adventure profile says that he's an athletic boy who also does well in school. His personality fits the military ideal. Between who he is as a character ("Yamato" even being Japan's ancient name), how Japan's military is, and proposed ideas for 02's sequel, it makes sense for him to become an astronaut.
As for Sora being a fashion designer, that shows her development as a character. She's taking more after her mother, instead of "rebelling" against her mother and the traditional ideas. The clothes Sora designs are modern clothing. They're kimonos. Kimonos are part of Japanese traditional tea ceremonies, along with flower arranging. In the epilogue, when Sora is shown with her designs, there are flowers in the scene. The Takenouchi family is traditional, and Sora's character development from Adventure through to the epilogue show that she understands her mother's traditional ideas and accepts them.
Now as for their relationship, that was planned right from the start of Adventure. Yes, the epilogue was originally planned to be at the end of the first season, rather than the second. (It was midway through Adventure that 02 was agreed upon to be a thing.) Kakuduo said that Taichi and Sora's (Taiora) relationship was only friendship and nothing more. It was always going to be Sora and Yamato (Sorato) becoming a couple. Only three script writers for the Japanese version knew about Sorato, which was why there was so little foreshadowing about the couple in Adventure. As for foreshadowing in 02, Sora and Yamato were background characters and the writers wanted to focus more on the main characters.
If you look through their relationship in Adventure, you'll find that Sora and Yamato understand each other. The same person who collected all this information did an analysis of Digimon Adventure episode 26
here.
The information can be found
here and
here.
I haven't found anything yet about Takeru and Hikari, but I haven't really gone looking. The only small bit of information I found was a brief mention that the writers of the series didn't want them to get together, but the animators did. After reading that, it is possible. Quite a few pieces of evidence about Takeru and Hikari liking each other more than just friends are bits of animation, and nothing really from the original series. EDIT: And this also makes sense with the fact that Takeru is the one
writing the story. Therefore, there wouldn't be much evidence in the written portion of Digimon compared to the animated form.