IMO that's completely fair, you MAY get crit with an ability once every 60+ seconds. [ which costs mana ]
ADCs WILL crit you once every 3 seconds, manaless, with lifesteal.
As an ADC you may crit on a 350 damage, single target 'ability' more than once every 3 seconds. But it's also far easier to itemise anti AD than anti AP. Big ticket armour items like
and
exist as well as items that help to weaken auto attacks against you like
and
.
A 1000 damage tibbers (completely possible) would crit for 2500 damage, after MR that's around 80% of a squishy champs HP pool, against some super squishy champs like Sona it could probably instakill.
If Annies whole combo was to crit she'd deal upwards of 5000 damage, which is undodgable, instantly. That would be by far the most broken thing in League ever, it would overthrow beta TF.
And then "lol muh escape
I think it's generally excepted that ADCs are super mobility creeped and eventually something will need to be done to tone down not just ADC mobility but the majority of the mobility in the game. I'm disappointed that you didn't even mention Kalista though.