Speedrunning PoGo for GoFest

So I fell off pokemon go back in 2020. Today is my first time logging back in since then. I feel like I might as well be starting a new game but I still have access to my old account. I'm level 40 with over 500 pokemon but I don't know how many of them are worth anything. I'm so overwhelmed with all the new things that have been added over the years, is it even worth trying to learn everything at once to participate in GoFest this weekend? I think it would be super cool to catch the legendary pokemon and participate in raids and max battles and all but I don't have any pokemon trained up or anything.