I don’t believe it is fair to call it a revival as when you see the release history from a meta point of view this has been the formula since generation 4. Gen 3 was an unusual experimental, growing pain era which reminiscent of an album that you don’t think is good but has a lot of forward-thinking game-changing and original qualities.
I relate with the OP post much as this is from a later time when I still remember seeing the debuts of Lugia and Ho-Oh LEGEND which from a rarity formula, presentation, and release standpoint changed everything about the release structure of the game. What we have now is, fortunately, more of the good and bad quality in quantity releases from a formula that starts with basic quality introductive models become increasingly more complex in style, creative capabilities, and artistic emphasis.
The outside collaborations (Mario & Luigi Gen 6, Edvard Munch Gen 7 & recent post stamps) have been it seems a generational tradition. Before that, it was promoting themselves within as a label only to claim sponsored collaboration afaik (Burger King, McDonald’s, Domino’s). The LEGENDS afaik were commission of artists outside of Pokémon (Shinji Higuchi known for being art director on Neon Genesis Evangelion) like the recent Urfishu (etc?) Studio Ghibli frelance artist used whom I can’t remember who if someone would like to roast this comment medium well are more then welcome.