So, the rule with writing anything on the site is that if you can write a successful article with it, it's fine.
At the moment, the classes are about containment difficulty, and the Foundation doesn't ultimately care if something could benefit mankind. I mean, a Keter could be human-beneficial, like the immortality spring.
The problem is that even human-beneficial SCPs are anomalous, which makes them inherently unpredictable. The Foundation doesn't know how they work, so there's no way to know if a seemingly-harmless object actually has some terrifying side effects. Thus, they contain it until they can explain it.
The exception is Thaumiel-class. Those are objects which have been deemed so beneficial to the Foundation (not necessarily to mankind) that they are worth the risks of using. Thaumiels are still contained and kept incredibly classified, though.