I mean, with this custom thing, you have that question as well with downside is you cannot pick up the knowledge from off the street.
I became the Kafka guy at my current company, it took me about a week of reading and every time I had further question, I didn't have to bother anyone, I could Google and get data I needed.
When it's some NIH thing, you have to bother coworkers and knowledge is whatever is in YOUR company knowledge base with no ability to get knowledge from outside the company.
EDIT: You could also leverage contractors or outside support if not homegrown software.
I became the Kafka guy at my current company, it took me about a week of reading and every time I had further question, I didn't have to bother anyone, I could Google and get data I needed.
When it's some NIH thing, you have to bother coworkers and knowledge is whatever is in YOUR company knowledge base with no ability to get knowledge from outside the company.
EDIT: You could also leverage contractors or outside support if not homegrown software.