This is true, lower Tiers have little AA because lower tiers are training grounds. Both for CV drivers to learn how to CV, and for surface ships to learn what CVs can do.
Tier 4 CVs are gated by bad damage and plane speed to make them more into training experiences. Tier 6 CVs have more damage and speed, but are still undertuned as the AA the exists isn't powerful yet. It's stronger, but not anything like what Tier 8 and up AA is.
So yes, this is different at lower tiers, though CVs are less of a threat there.
I wasn't referring to "resources" like HP or Ammo. Resources in this case is better thought of as "Players" or "Player Positions".
By having players position closer, you gain Defense, but lose Offense. There is no perfect choice, because you are given a situation that is complex and requires dynamic choices since you don't have enough resources (Players) to cover all the problems at one time.