Players usually ignore reactiveness and don't use it.

For example, using raid-wide mit or Reprisal is reactive. Using Nascent Flash, TBN, cover or clemency on other players is reactive. Interrupting attacks or stunning them is reactive. Many players don't do these things.

We used to have specific mitigations like you are suggesting - one for physical attacks, one for magical attacks, but players started saying "well they are useless some of the time, please make them work on everything". So they did and now a lot of the mitigations do the same thing but with a different %. What remains (Dark Mind which only works against magic), people are still asking for it to just be a generic mitigation like all the others even within the last few days.