i worry that dni culture is leading to people not acctually understanding what the things they are talking about actually mean
As they are currently used, DNI's are just virtue flag waving. I always roll my eyes when I see them, especially when they're accompanied by death threats or slurs against the 'icky gross unwanted people.'
The thing about a DNI is that it requires two things:
The person you're attempting to dissuade actually being overt and/or public about their beliefs, values, caste, ect.
The same person actually respecting that DNI. Which the majority will not. Nazis do not care if they make you uncomfortable. TERFs so not care if you don't want them to read your self-insert fanfic. Religious bigots believe God wants them to harass you.
And, sure. DNI's are somewhat effective in terms of a symbiotic co-existence in online spaces between castes such as anti and proshipper, for example. Because in most cases if a proshipper sees themselves on your DNI they're just going to block you. But generally, that happens anyway. Most people do not actively want to interact with someone who believes they're an evil person, pedophile, ect.
DNI's at the moment are just another way for people to gain social brownie points, feel better about themselves, and flag wave to other likeminded people that they're not 'one of the bad ones' or 'one of the freaks.'
"Oooh but if I don't have a DNI about Nazis you're going to assume my blog is welcoming to them!"
I don't know about you, but personally, I have never assumed that. The default is that Nazis should not be welcome anywhere. I have never looked at a blog without a Nazi DNI and assumed said person was a Nazi or supportive of Nazis. The global default should be that being a Nazi is not acceptable anywhere, at any time.
"Whhah but I don't want icky proshippers reblogging my aesthetic autism moodboard!"
I could honestly not give less of a fuck. There are much bigger problems in real life and online than some 'icky evil (not) pedo' reblogging a few photos you stole and compiled and are trying to claim rights over.