“NIH” from the manager’s perspective would be more like contracting a professional bookshelf maker to build a bookshelf for you. They go to the lumber yard, select wood, cutting, planing and nailing it together to build a perfect bookshelf.
In the IKEA case you get something that works but might not fit your requirements exactly. In the NIH case you get something that is exactly what you need (hopefully), but will be much more expensive to construct and will take orders of magnitude more time.
There’s no right or wrong answers. Sometimes an IKEA bookshelf is suitable. Sometimes it isn’t.