Let me be clear, I'm a big fan of rat's passive and I pitched its return when it was removed SEVERAL times. And even if it was terrible and rat was useless because of it, I would still prefer the passive over its previous version. However, just because I love it doesn't mean I can't criticize it, and just because it's unique doesn't mean it's good.
Saying "if you don't like it then sell it" is silly because you're literally saying "well if you think this char's passive is bad just don't have a passive at all" instead of suggesting ways it can actually be improved upon.
And last things last, yes, it's "typically" better than other items but that doesn't justify the lack of a slot it takes cause it's about the item passives as well