To be fair, much of the modern news cycle comes from Reddit. When I worked as a tech journalist years ago, we had half a dozen bots watching relevant subs and alerting us to breaking news. We'd clean it up, fact-check, call sources for comment, and do all the "journalistic" stuff you'd expect, just like with any other story, but Reddit was absolutely part of our workflow. You've got to look for news wherever the news is happening, be that a press release, a leak on twitter, or a convo on Reddit, and frequently it happened to be Reddit.
These days you even have tictokers cutting out the middleman and straight-up reading r/AmITheAsshole posts over Minecraft footage for views. Is it any surprise that news sites are commenting on their content firehose being turned off?
I do too, but this thread is about ways to filter or block content so I'm not really sure what that has to do with it?
I'd love a way to filter by keyword, which the Reddit Enhancement Suite and some of the 3rd party apps allowed. Maybe the upcoming Sync for Lemmy will port over its filters by domain, user, subreddit, flair, and keyword.
As for Reddit posts invading Lemmy, it seems like most of them are contained to c/reddit and c/RedditMigration, so blocking those two should fix most of OP's issue and that's easy enough to do without any extra tools.