Why are critical chance/damage so rare?

I really want to try make something more critical damage focused for a fire build but I just havent managed to get any decent crit/crit damage affixes on my gear that are high tier.

Have they changed those affixes to trigger less frequently? I might get a decent crit affix on a dropped weapon but its obviously garbage without +4-5 on spells (And recomb just eats them lul)

As described by the poe devs, the passive tree is there to boost the base stats you get from gear, its hard though to boost crit when you just cant get any decent affixes because it is so rare.