It does, but not to the extent that changing type charts does. And tell me how much of an effect Deoxys S or Wobbuffet had on your playstyle after the initial hype. If Dragon was suddenly resisted by and hit SE by Poison (just to address both of the types X-Act mentioned), don't you think Poison types would have a dramatic increase in usage. Gengar might replace Garchomp as number 1 (yeah, Gengar's a Poison-type, even though he never uses it). And that's just changing the relationship between only two types. Imagine trying to do this for all 17 types.