i think you only got used to this boosted rune
ADCs (at least hypercarryes) are not supposed to trade with a poke support such as sona during their laning phase,the insane sustain of footwork made it possible since they would just heal back the damage while the support can't (at least not that much and they still have to use resources),making it pointless
ADC players just have to get used to respect a poke support damage and play around his kit instead of harrassing them like an angry monkey every time they are in their AA range
anyway if you want some sustain you can still get it from items (
) or runes such as taste of blood,you just have to give up something now as it is supposed to be (you want sustain? so you give up damage/utility,getting **always ** bot was unhealty)