what kind of end user would use this though?
A paediatrician would be a good end-user or plenty of companies offering products and services relating to new-borns and young children... medicine, clothing, toys, diapers, etc
Could be a forum, shop, etc.
It's a nice name. But if the OP paid $xx,xxx, for resale... depending on exactly the amount paid, there may be small room for profit... or maybe none at all.
Firstly, .net is not dying. It is being used as a good alternative to .com or the end-users ccTLD, if already taken.
and baby stores would rather use their own brandable name than the word baby
That's true. Companies that have a large range of products and have built a trusted brand, tend to use their main domain to promote their products. What better stamp approval could they want, than from their own brand that has been around for years.
For an entrant into the market, a name like baby.net would be great for them. It's makes a solid brand name for their products/services, in such a case.