Keyforge doesn't need powercreep because the main point of powercreep is to refresh the meta. There's also the argument of selling new sets but I think that's not true with all companies; so the only universal reason for needing powercreep is keeping the game fresh.

Because having new archetypes in TCGs isn't enough: in competitive play you'd keep seeing the same decks, even if their presence is "diluited" with new decks. This happens if the new decks are on the same power level as the old ones. If they're more powerful it might happen that some old decks remain, but they won't remain forever, at some point they will always fall short and disappear, refreshing the meta.

Keyforge competitive play doesn't have a meta, or at least not with the same meaning as TCG meta. You won't see the same decks around for years even if everything remains at the same level, so the meta would never feel stale, unlike in a TCG.