I get what you're saying, but I wouldn't say it was pointless as a whole. Maybe it's because I'm looking at it from a slightly different perspective.
Karma did help push engagement, in fact, the system worked.
People cared about this number, and started to optimize their behavior such that they receive the largest amount of karma in the shortest time.
Since being active by posting / commenting facilitated getting karma, it helped produce a lot of content and made people interact with each other.
The problem with that is that it wasn't tied to quality (and couldn't be). As you said, that encouraged regurgitating the same meta over and over. It never incentivized good content, just quantity.
So my conclusion would be more like: Karma was pointless for animating users to create good and thoughtful content.
Instead it helped driving engagement forward, but at the cost of somewhat turning people into bots.
Posts receiving upvotes / downvotes is okay, but I'm not sure in what way reputation - or karma - should be displayed for a user account, publicly or privately.