I'm mostly watching seasonal stuff so it makes it a bit more challenging. You'd need to know what comes out every season and scrape the discussion threads for that. https://anichart.net/ is an example of listing all shows each season. I wonder if it has an API somewhere. There are also rewatch discussion threads that pop up for older things that would be nice to have. Yeah, it's fairly challenging :). Could possibly scrape the top 250 shows from anilist/MAL which would cover rewatches. But seasonal would be the most useful.