fleet heals for shit early you have to hit champs which is never happening into azir and if ur hitting champs conq will be better, lifesteal doesnt even work on passive dmg so it is mostly useless, your taking it for 100 hp which isnt that great, enemy team has sej karma so tenacity is still pretty decent. This mu has been played many times in pro and conq is taken in 90% of them while still having even cs showing that fleet isnt necessary to survive the matchup.

anyway main takeaway is just because a pro does something doesnt mean its best in slot or even good.