For most shiny hunters it might be worth it to you(as long as you are one of those people who shiny hunt alot and like shinys I think you'll find it pretty appealing). The dlc gives some access to some legendaries and not all but some can be shiny such as:
-Latias
-Latios
-Cobalion
-Terrakion
-Virizion
the Pokemon that you can get but cannot be shiny are:
-Darkrai
-Genesect
-Groudon
-Heatran
-Hoopa
-Keldeo
-Kyogre
-Magearna
-Marshadow
-Melmetal
-Meltan
-Meloetta
-Rayquaza
-Volcanion
-Zeraora
some of those may be worth it as well as the access to Pokemon that cannot be caught in the normal version of the game mostly paldea and the dlc also makes fossil Pokemon SO much easier especially with a turbo controller
so mostly it is pretty worth it for shiny hunters and mons for competitive play Pokemon(hopes this helps you!)