Comment by poomer

I do not remember the specific metrics, but there was a big focus on the fact that their CPC/CPM/etc was lower than alternative social media, meaning advertisers put less value on clicks/views from Reddit than other platforms. And they believed this was because their ads were not targeted enough since there was (is?) no fancy ML models behind it, advertisers could just chose some basic rules for what subreddits they want to target.

To solve this they were building out a huge ad relevancy team to target ads at users using posting history, similar to Meta/LinkedIn/etc.