There are 3 main culprit for Immunity as a widespread system for being a very crappy design
imbalanced distribution of resistance/immunity within the bestiary
also not being able to deal damage is a bad design in general
finally, pairing all of this with the synergy system that kills Hybridation and forces you to specialize
So it’s either rework the synergy system to be more general
Where skills synergize eachother not only based on their damage type but also other shared properties
So you could be a fireball build and still be able to tackle fire immunes because your ice bolt would be buffed by the fact it’s a projection like fireball
OR
JUST do away with immunities and just apply the RESISTANT system instead which is as hard if not harder but you can damage 100% of the time