No need, there are already several projects that have been scraping and downloading posts and comments for archival reasons for years. It's just a one click download.
After killing the old reddit. I don't think scrapping is very effective, at least for the comments. Visibility of comments on web site is pretty horrid.
The API is still there, and it must still be usable without paying, since the mobile app is using it. So setup mitmproxy on your iPhone and sniff the traffic to figure out how it gets its key, and then replicate that in your scraper.