I have never seen a situation where a blog was useless when done properly.
You have said what the site is not about. That really doesn't help in answering your question.
A blog doesn't have to be fun to help. "Fun" has nothing to due with a blog being useful or not A blog needs to provide useful information that people are looking for. If it does that then it's useful.
SEO is not based on it being "fun". SEO isn't based on feelings period, it is based on data analysis. Most sites I work on are no fun at all, they require work to reach page 1.
If you're not basing your decisions on analysis, then yes, you're incorrect.