Why does everyone say def/spdef is useless?

i just don’t get it reading up on it and the formula every 6 def/spdef gives you 1% effective hp vs the respective damage type. So take the emblems you can reasonably pump out say 20-21 def or sp def with an emblem. Which as raw stats would work surprisingly well on attackers or speedsters who don’t have much of that stat at all.

i get that raw hp is definitely better early game but isn’t there something to be said for a tyranitar showing up with +10 def which for him with his passive effectively gives him 165? Which is 27% more effective hp vs attackers? Slap on sand tomb and you get a chonky boi