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If your idea of creativity is seeing how many different concepts they can mash into a single design then gens 1 and 5 are easily the least creative batches since a lot of their Pokemon were based off a single idea, usually an animal or kaiju of some sort.
If anything Pokemon designs are getting too creative for their own good because they keep trying to do a dozen different things with each one, which is how you get things like jobmon starters.