Is an acorn, or an appleseen, or any other type of seed generally considered to be "alive", in common terminology, before it germinates? Prior to germination, it's possible, in the right environment, for a seed to exist without changing or growing for a substantial length of time. Once a seed has germinated, however, it must from thenceforth either grow or perish.
I would liken a plant seed to a gasoline engine with a fuel pump, magneto-based ignition, a weak battery, and no alternator. As built, the motor contains everything necessary for operation except fuel; if fuel is present soon enough after the starter is activated, the motor will be run for a long time. If fuel is not supplied soon enough after starting, or if the fuel supply is ever discontinued, the motor will die and not be restartable. As shipped from the factory, the motor's static state contains everything necessary to allow the motor to operate once given fuel and activated. Once the motor is started, however, the kinetic energy of various parts of the motor becomes an essential part of its operation. If that kinetic energy is removed, even if no physical part of the motor is damaged, the motor will become useless. I would posit that a human zygote/embryo is somewhat similar. Initially upon fertilization, the static state of the embryo holds everything necessary to 'start it up'. Even if one removes the dynamic aspects of its state by freezing it in liquid nitrogen, the static aspects of its state will allow it to restart when it's thawed. Once the embryo has implanted, however, then the dynamic aspects of its state become critical and if they are ever lost, the embryo will die.
The seed may appear to be innert, but it's not. The embryo is carrying on a very slow metabolism within the seed. Eventually, if not planted in the proper environment, it will die.
The animal, including human, embryo, draws nutrients from the environment. The human embryo is never dormant - germination is immediate, from fertilization. If he or she is not in the proper environment, he or she will die, as we all would. The environment doesn't make the species.
Your analogy fails on the fact that the technicians who carry out IVF purposefully create the environment to enhance the growth of the embryo - at least for as long as they desire, in practical terms for at least 5 days. The limit is the wrong:
The responsibility of the ones who bring the oocyte and spermatocyte together in order to cause fertilization is to ensure the best conditions and environment possible for the nascent human being, without a limit, and certainly without a planned death.