in my experience, reddit advertising has been idiotic for several years.
I go to a basketball subreddit. there are no relevant ads about basketball. not local team tickets, not streaming services, basketball equipment, basketball merch, or even a video game.
I go to a subreddit for a tv show. it's similar. There are no ads or links to buy dvds or tickets to a convention or anything related to the show.
They could totally target advertising based on subreddit and they don't.
Easier said than done. Payroll systems do this automatically