Few people accept it but most people love reinventing the wheel.
Sometimes an existing wheel design is perfect for our use case, or at least good enough that creating a new one isn't worth the effort. Sometimes a tweaked wheel is what we need. Sometimes a radical departure from established wheel design is required to make a new machine possible.
Build vs buy is an eternal question, and it's reasonable to examine and reexamine it for any project. But "reinvent the wheel" is just hyperbole.
You greatly overestimate people's knowledge of wheels.
Your complaint about the phrase seems to be that it doesn't well describe the process of adjusting another design to work better for a specific use-case. But that's not what the phrase is trying to describe, it's literally describing the problem where people reinvent that which absolutely does not need to be reinvented.
In the case of rewriting an application feature for feature in another language, that may or may not be a good idea. Maybe we're switching from an interpreted language to a compiled language because we need better performance. Maybe we're replacing a huge pile of impenetrable bash with a well organized Python app. Maybe we're taking advantage of a library that's only available in another language. Maybe there's a good reason for the rewrite but it's so much work that it's still not worth it. Maybe it's just a engineers wanting to use the latest toys because it'll look good on their resumes.
It's totally legit to question the need for a given project. But the phrase "reinvent the wheel" is just scornful insult. It adds nothing to the discussion, and in fact makes it harder to discuss trade-offs.