You’re right about the plastic, but just drop the enlightened snark.
As for pottery, forging, casting etc.: completely different processes, different requirements, “vibe” - may not be possible for OP (ever tried operating a forge in a New York city apartment?), might not be aligned with their skills / interests, financial situation etc.
So, what remains is the question: do you believe 3d printing with plastic should be outlawed or at least strongly regulated as a private hobby?
Great project, I like that you went all in and installed the solar panels - there is a nonzero chance I would have tested it with only a battery first, therefore creating a suboptimal solution that would have stayed around far too long, endlessly bugging me in the process.
Just one remark: the mailbox is so nice, you should definitely route a channel in the treated pine to hide / protect the blue cable better, that’d make it perfect.