I don't disagree with you there, he's in a wonderful spot right now. The sustained damage, build-up-to-massive-damage approach is the best for Mordekaiser, and much easier to balance around, in my opinion.
Riot wants to keep his duo-lane identity in tact, but the meta just doesn't allow two melee characters in the bot lane, especially when the carry has no form of cc or mobility (or even slows).
Almost every adc played right now has a slow or dash/jump/displacement. Mordekaiser has none of that, which makes him super heavily reliant on his support, as well as making him vulnerable to ganks.
In top lane, that doesn't matter as much since your opponent will also have to get close to deal damage. But bot lane requires more range in order to survive, farm, poke, and trade effectively.
Just my thoughts here.