What about them, exactly?
I think they’re an interesting thing to have. There’s an obvious moral dimension to the creation of new living things, or to repurposing created life thousands of years later as we do with ancient Pokémon that may be artificial like Sigilyph and Golett – let alone whatever Spiritomb is. Ecologically they’re curious since you wouldn’t expect an artificial life form to fit neatly into any preexisting ecosystem, although for some of them, like Grimer (if we can consider Grimer “man-made”; it is a byproduct of human civilisation, at any rate) there is a ready-made niche for them to fill as a result of the circumstances of their creation. The technological level that must go into creating Pokémon – even by accident, as might have happened in Voltorb’s case – is interesting to think about, particularly in terms of whether the ancient ones were created by “technology” as we understand it or by some mystical practice. And equally curious are the Pokémon who aren’t explicitly artificial but look like they should be, like Klink and Magneton – what’s their relationship with human science and engineering? There’s a lot of different directions you could potentially go with them.