I can say as someone who runs a small niche subreddit, users have been finding my sub at a much increased rate in the past 6 months, I suspect because of the "related subs" boxes that auto insert themselves in the new design.

If their aim was to improve the discoverability of smaller subs, they've achieved it.

It's not all bad of course, it's a complex product so you can simultaneously delivery useful features while making the design / usability worse.