I wanted to run Reddit ads after to target users of a certain game after a big expansion launch. My site had a bunch of time-sensitive information that 1) was useful to the users of a specific subreddit, 2) would be useful for a week or so after the launch, 3) while it had a successful submission, I wanted to promote that submission for about a week afterwards to more people could see it.

I put up a reddit ad for that submission and Reddit took 4 weeks to approve it. At that point, there was no point running the ad anymore.

Another time I wanted to advertise to a new game that had a brand new subreddit to match but it was huge - 100k plus users in a week. Reddit simply wouldn't permit me to advertise to it because it was new.

In my (limited) experience it feels like Reddit isn't making the money it could be because it doesn't want to.