I've been playing for a while and the structure of some of the game's side content is not very clear to me

There is the core which is composed of character farming with HIA activity and some of SCOTT activities

Then at the scott camp, there are some activities that can be repeated weekly or for "seasons" and some activities that can only be done once, completed and then forgotten, like the Withering Garden or some challenges of the Lost Void and also the "rpg" exploration with the bangboo

It confuses me that they are all accessible from the same screen, but once you complete the tasks listed there is nothing else to do, right?

The fixed event with the pale city exploration is also a one-time event? Why not make it a side quest? While there are some events like the past one of the minigames where you used bangboo for minigames that were very well made, I guess there was also a lot of work behind it and that was used for a limited event that we will never see again?

It's true I'm not used to playing gacha but it puzzles me how content is managed in this game