From everything we've seen, Ralph treated Sandra like shit, not only the "call you an uber" stream (where she seemed used to Ralph's behavior/having to find other people to help her), but also the texts with Faith where he makes his terminally ill mother make him pancakes because he is sad (and other ridiculous shit like that), there is also the fact that he decided to abandon her when she was at her worst point health wise because he thought he was going to get a threesome out of it (after mooching off of her for 30+ years and not contributing a dime), there's the fact they lived off her SSI because he was too lazy to get a job, the fact he didn't help her when he was making 15k+ a month on YouTube, the entire final saga with Sandra and the vaccine, etc.
But I think one of the most telling things is Ralph saying that everyone has "unguarded" moments where they speak to their mothers like that. No Ralph, that is not the case, people might have arguments with loved ones but that type of behavior isn't really something everyone goes through with their parents when in their 30s.
It's sad because I do believe he probably regrets all of it, but like Ralph likes to say, it is what it is.