"immobile melees shouldn't have items to overcome their weaknesses" says the marksman
as the marksman enjoys his comfy selection of
to reduce, delay, or otherwise overcome burst and assassination attempts and
to give them a second chance if they eat a CC spell
(notice all of these items also have modest to very good offensive stats too)
to counter burst on my adc so instead of dieing for there miss position they killed the enemy team. Shields from supporting champions are also to blame for adc strenght, and if supports could/would give movespeed to juggernauts I think they would carry far harder.

Slithering passive intensifies
is a thing and
+
crit +warlord as well as the mentioned
.
.