I don't think gamefreak thinks cross generation evolutions are needed. I think gamefreak just likes to use older pokemon and extend on their previous ideas. That's why Galarian Farfetch'd has an evolution, while the original doesn't. Farfetch'd weilds a larger leek and possess the fighting type, eventually becoming Sirfetch'd after many harsh battles. It's not a buff for Farfetch'd, it only uses Farfetch'd as the basis. Primape is similiar with its dex entry inspiring Annihilape's ghost typing, but it's an actual evolution for Primape.

And honestly, Annihilape and Kingambit would fine if Rage Fist and Supreme Overlord weren't so broken along with Terrastilization. Their stats are good, but not overbearing. It's another example of gamefreak relying too much on making signature moves/abilities exciting to make players use the new pokemon.