I don't think building compilers is that bad, tbh. It's very difficult to do this without realizing it.

I've written a dozen different programs that might be considered compilers; some very simple, others very complex and whose life continued once I left the organization. Writing a functional compiler that provides the needs of the organization where existing tooling doesn't takes discipline and focus on what you actually want to accomplish. I don't know what "defining a struct inside a loop" might mean and this strikes me as, very obviously, having no clue what you actually want to build.

Perhaps the issue is not building a compiler but rather the lack of focus to begin with.