For me at least, this is probably the only place I'm on frequently and I'd love to know how to block keywords, but I couldn't find such an option (afaik you can only block people and mute categories
) So I guess it's possible someone even more technically inept than me might have trouble figuring out how to curate their experience? :'D
Another factor contributing to reluctance to block might be 'seeing the block button as condemnation'; like 'If you block me, it means you hate me' or 'If you block this content, it means you're morally opposed to this content even existing'. So using the block button makes you feel judgmental.
I think it'll do us all good to internalize the notion that blocking is not necessarily judgment; it's just a boundary, nothing more, nothing less. You can have boundaries for whatever reason, even silly ones; you don't need a serious, moral reason to enforce a boundary.
EDIT: Had a bit of a think about echo chambers - I* think that's more to do with people blocking out the other side's opinions while simultaneously not blocking out equally vitriolic opinions from one's own side. I have respect for blocking out the other side; and heck, I understand the need to vent as well** - but I don't think it's healthy to be immersed in an environment where everyone's constantly outraged and egging each other on to be outraged, even if they're all outraged about the same thing.
That's what an echo chamber is; where your anger is constantly echoing off the walls and bouncing back to you, where displaying your anger more and more intensely becomes an almost 'fun' activity of ingroup solidarity. It's not merely an environment where the opposing views are absent; if the vitriol from both sides are absent, it's just a nice, quiet chamber 
*
personally, at least; I know there are lots of people who use the echochamber thing to guilt-trip people for not wanting to interact with random internet strangers' opinions
**
So how to vent without landing yourself in an echo chamber? So far I guess my best idea is to limit your venting time; interact with the echo chamber briefly to confirm you're not alone in your frustrations and then walk away, telling yourself 'okay, I've confirmed with my own eyes that other people care about this as well, now it's time for me to move on to nicer things'. But that's easier said than done, of course :'D ... I wonder if you can block content so that it doesn't appear on your feed, but you can still interact with it when you want to but still keep it blocked 