It would be over engineered if one could design a system providing similar functionality using less hardware and less software.
I challenge you to design a wireless doorbell that has a user-configurable chime, in a way that uses less software or less hardware than mine. You couldn't.
In fact, if you did market research like me you would find that 99% of similar products have vastly more complex hardware or software or services being them. They break when there is no Internet. Some work without Internet but don't work when the local Wi-Fi is non functional. They don't immediately get back online after a power outage. They need regular software updates during which the chime can't play. These are over engineered things. Not my product, because mine has none of this complexity or faults.
Challenge accepted: "Similar functionality" here is the same doorbells that have existed for over a century. Done. :)
If the requirements and constraints come from you, then saying "those are the requirements" doesn't settle anything. And is the same excuse people use for the over-engineered solutions you don't seem to like.
It is over-engineering compared to a regular doorbell, period.
OP stated it requires a user configurable chime. This is not a regular doorbell.