Majority of the keystones are auto attack oriented....

Press the attack: needs auto to proc while damage thereafter can include abilities. Letha tempo: spells can be used to setup, but all damage is done through auto attacks. Fleet foots: plain auto attacks to proc. No abilities. Conqueror: abilities can be used to setup, but auto is the final proc.

Electrocute: both auto attack and spell oriented. Predator: both auto attack and spell oriented. Dark harvest: plain auto auto attack. No spells Hail of blades: just auto attacks. No spells

Summon Aery : both spells and AA. Arcane comet: just spells. Phase rush: both spells and AA.

Grasp of the undying: both spells and AA, but AA decides the final proc. Aftershock: only spells. Guardian: only spells.

Glacial augment: AA and item actives Kleptomancy: combination of spell and AA, tho AA is the final deciding proc. Unseal spellbook: completely neutral.

As you an see, out of the 17 keystones, 13 of them use auto attacks to finally proc the keystone, while 5 of that 13 can use spells to setup the proc like lethal tempo for example.

Conversely, 7 of 17 keystone are proc with spells. None of the can use auto attacks for setup.

It’s kinda sad because while the game does have more AD champs, all champs have auto attacks and spells even if they are not a mage. But with the current setup of keystone, auto attacking oriented have a much larger variety of keystones to choose from, while spell oriented champs (not only mages, but supports and Ad casters for example) don’t.