So what happened is that I saw someone on Twitter wondering if they should catch up on Made in Abyss, because they'd heard (and seen from screenshots) that some brutal and unpleasant things happened to the characters and were partly wondering if the show was being gratuitous with them. This sparked a stream of thoughts on Twitter:

Made in Abyss's latest episodes are wrenching and powerful, but are they necessary? And is this a question that matters?

I don't think MiA's events were gratuitous or overdone & things mostly focused on the emotional impact. The body horror was probably needed.

'Body horror' is not quite the right description for 'people getting hurt badly', but Twitter has length limits. The show definitely presented the situation in a way that was intended to make it wrenching; this was not pleasant, pretty, antiseptic stuff, it was visceral and cringe-inducing and painful to watch. Within the context of the episodes I don't think the show dwelt on things in a way that would have made it torture porn or pain porn; the focus was very much on how all of these horrible things affected the characters, especially Reg. The horrible things got shown to give Reg's reactions context and weight, and the show framed things claustrophobically to focus on this (cf, which has spoilers).

(See Nick Creamer's description in his week in summary post for more concrete stuff, but note that it has spoilers. He calls episode 10 'viscerally excruciating' and I would have to agree with that.)

As for the overall necessity, we have to wait and see how the story develops. I think there are early promising signs based on Nanachi.

That the events in the episode are non-gratuitous doesn't necessarily mean that the episode itself (and those events) are actually necessary. We won't know how necessary the events were overall until we see the story and the show's themes develop more. However, I think there are already clear promising signs, because the course of the story has clearly shifted after the events of episode 10.

Story elements don't necessarily have to have a point; they can be there for emotional impact. But terror and pain are empty w/o a meaning.
Made in Abyss certainly delivered emotional impact. Whether it used too much terror & pain for that is still open and also a personal call.

This is the question of whether the question in my initial tweet even matters. If Made in Abyss episodes 10 and 11 evoke such a strong emotional reaction from us, do they have to be 'necessary' in the larger scale of the plot? After all, stories are in large part about the emotional reactions they evoke and episode 10 certainly did that.

I don't have an answer but I do have an opinion, which is that some ways of evoking emotional responses are cheaper, easier, and more shallow than others. Kicking a puppy is a bad cliche for a good reason. Tormenting characters just to get a reaction from the audience is lazy and unappealing, and in the process it lessens the impact of the entire work. I personally don't think that Made in Abyss has crossed this line, but then I'm a jaded anime watcher.

(And I will admit that there are caution signs in some things in Made in Abyss, things that came up in passing that I'm not sure really needed to be there. Some of these questionable bits have been there from early on in the show.)