To me Reddit is a website, people keep referring to it as an app, but I have never used an app for it. It works best in the browser.
I think the biggest impact, though, is some moderators rely on tools/clients to make their (voluntary) jobs easier. If those tools disappear, then a lot of these subreddits will probably shut down for lack of moderators. And I heard that /r/blind mods literally cannot use the existing Reddit site/apps.