Granted. At first there are no drawbacks, however when Nintendo learns their copywriter material is being used, they get angry and sue Reddit for copyright infringement.
Countless hours are spent recoding and trying everything, but because of your wish, the upvote button cannot be replaced with anything else. After several months of Reddit being shut down by the government, Nintendo and Reddit finally come to a compromise where Nintendo owns a large stake in Reddit, and gets a large portion of ad revenue. Nintendo uses their newfound large stake in the company to their advantage, and since they are already unhappy with their unwanted foray into social media, advertisements on Reddit quadruple, and there are now pop ups.
Reddit usage steeply drops as people move to Instagram, so they change the system and instead every upvote costs money, however downvotes are unchanged and still free.
Now, every post is far in the negative for Karma and all OG Reddit users and creators are devestated. In order to circumvent the system, Redditors now consider a ‘downvote’ and negative karma a good thing, since nobody wants to pay a dollar for a lousy 10 pack of upvotes.
All old Reddit users who used to be obsessed with Karma are forced to start new accounts, because they don’t want the 100k+ karma because downvotes are the new vogue. Their new accounts have less followers, and their OC is much more difficult to find. After over a year of trying to make the new system work, it fails. New apps rise, but due to a lack of communication they all fail to fill in the void left by Reddit.

Since hard-nosed redditors do not want to become instagram normies, they turn to the back-allys where original content used to go to be reposted to hell. All redditors switch to IFunny and Reddit finally goes under. Congratulations, in around a year and a half you’ve made us all use IFunny with their biased “Featuresets” for our memes. IFunny becomes the norm for everyone and after much adjustment, ten years from now nobody even remembers Reddit anymore. IFunny has taken over.