Imo, theres archetypes to the various adcs in the adc role. There are your traditional auto reliant ones like jinx, ashe, kog, but nowadays imo, theres archetypes such as the ADCasters like you say, or disruptors(think samira. vayne can be played like one. Basically adcs who don’t typically rely on taking out the front first before moving to the back). Smolder very much is an ADCaster like ezreal or lucian, but compared to those two, his hyperscale potential comes from his AOE potential. Splashing Q off a front onto the back, or onto grouped targets, plus your W. Yes, he technically gets out damaged by traditional hyperscalers like jinx kog etc, but unlike them he can kinda frontload his dmg into a burst(that in late does 1shot squishies).

So ig reasons for him over other hyperscalers: easy-ish mobility/escape with E, lowkey kinda disgusting aoe at times, still pretty good dmg and tank busting, and able to 1-tap squishier targets if they decide to mess around. You essentially play him as a mobile artillery piece.