Hell no
A little bit of a disruption, but it wont ruin blogging at all. In my own experience doing searchers, the shit that google suggests on reddit is often trash.
Do some searches about affiliate marketing and SEO, you'll find reddit posts ranked on google like "I just realized my website I created during google has earned me $4.70 in affiliate commision over the past 3 years" then all the other failures on the subreddit that never made any money upvote it and say how amazing it is. Normal people will recognise reddit is a shit website with shit advice mostly written by failures and losers, click the back button, and go find a blog post about an actual relevant SEO case study(well, in context of that topic, for example). Not all of us want to take advice from homosexual basement dwellers and know it all teen agers with 0 life experience. Just like a blog, you'd still need actual good content or you'll most traffic will still bounce.
Sure, some topics reddit may actually be useful for, though generally, most of the time there's a much better blog post.
The current niche and previous niche I've been working on have nearly no reddit results in any of the niche searches.