i think replacing the r slur with words like stupid, idiot, or synonyms is a pretty uncontroversial change since that's basically how they're used - the only reason it's that specific word rather than some other synonym for stupid is because of edgy internet culture of the time. and imo there's enough other cultural signifiers of that kind of internet culture that are overall more interesting and meaningful, plus even the comic itself grows out of that verbiage. whether the specific replacements are themselves good is a separate issue, but i think the concept itself is fine.

with some other things the mod changes it's different - as some people already pointed out, some of the characters are ableist, and it is part of the point. i think there's an argument to be made for example karkat calling nepeta autistic is not just hussie using autistic as an insult in place of a generic insult, but rather karkat being deliberately an asshole. plus, there's something to be said about karkat special interest in quadrants vantas calling nepeta autistic for being weird or whatever, especially with the parallels between nepeta's shipping and karkat's totally-not-shipping.

and i also will forever mourn the future arachnidsgrip joke.

generally speaking the mod doesn't differentiate between "tasteless casual ableism that made its way into the comic due to the specifics of the internet culture of the time" and "ableism existing as a plot beat/character point". and i kind of get why, it's hard to make hard lines about this stuff, so they ultimately made their own calls and let people decide whether this was something they wanted or not, which i think is a fair way to go about it.