One of the largest issues with the karma system is not the karma system itself, but our relative lack of things that one can do with their karma.
A regular player quickly accrues (on average) enough karma to buy everything thrice over.
Otherwise...
* Karma serves to keep the rarity of certain races in check. Given that human is our most popular species (by a margin of over 50% according to survey, IIRC) it seems to be doing this function admirably. While there are instances where there is a "higher proportion" of certain species in elevated command roles, this is happenstance - the vast majority of the crew is, has, and always will be human due to simple metrics (most players play as them, all new players lack other species unlocks, and simple game mechanics).
* Karma serves to gate some of the more important jobs. If you want to play Blueshield, NT Rep, or Magistrate for instance you will need to at least put a fair amount of time into the server - this makes people who elect for these more sensitive roles at least somewhat familiar with the backdrop they're playing against compared to fresh players.
* Karma serves as an anonymous token of appreciation/admiration. Nobody is entitled to it or required to give it - it's something nice that someone can award you if they feel like it. The absence of it does not imply someone is somehow a terrible player, and the presence of it does not imply someone is a great player. Having karma merely demonstrates that select individuals found (on whatever unknown grounds) your actions worthy of merit.
As a suggestion...
* Add the ability to purchase extra loadout points (5) for 50 karma. (also add more things to the loadout options in general)
* Add the ability to purchase a single antag token for 100 karma (these are only eligible for minor traitor roles, for reference). This is probably a bit more contentious, but it's literally one token.
or
* Add the ability to spend 100 karma for a fluff item. This won't impact donations for those concerned, as the presence of more fluff items will likely drive people to want them more - meaning we'd see most people opt to donate rather than wait to accrue 100 karma.
Really, in general just add possible expenditures to karma that don't deplete in a single buy, and are 'renewable' karma dumps. This would not only give karma a more useful purpose, but it would also make karma-locked species more rare because people would be driven to save for other purposes.