In previous editions of D&D it was possible to have two base forms or (in some editions) a creature 'template'. In 5e the base form is important and always singular: many spells &/or magics only work on specific creature type(s). The problem we encountered: can a Simulacrum be Reincarnated? You will note that the Simulacrum specifies that it can only be cast on humanoids and the spell claims it creates an exact duplicate. That said, this exact duplicate cannot accept healing &/or learning. What's more, this replicant has only half the hit points.
With Reincarnation you will note that the recipient creature must be a humanoid. Previous editions were much more open to include many other living creatures but 5e is very specific. Thus, this spell will allow the reincarnation of exotic creatures such as Xvarts, half-dragon kobolds or even Nagpas - but not any beast, giant, or fae, regardless of how identical they are to humans. But i digress. The long and short of this: a construct will NOT be reincarnated. It is devoid of the life required to incarnate in the first place (in fact, it is odd that a construct is considered a 'creature' and not a 'magic item').
What is odd about D&D constructs, they are far more alive than most people. They heal after a short or long rest. The Simulacrum does not get this. Many a construct (or animated dead) does not suffer exhaustion - but a Simulacrum does.
Truth is, the 'Real World' concept of Reincarnation would be poor source material as many faiths believe that all animals, insects and possibly even plants return in some justly-deserved shape. Does your dog have a soul? Does your cat have more of a soul than, say, Mike Bloomberg? How about the spirit-in-car-golem Herbie the Lovebug. Why not reincarnate this car... again?
Thus / the Question: does anyone know if the 'creature' created by the Simulacrum spell is considered a humanoid or a construct?