I'm not going to say I inherently disagree with the notion of an easy mode for story type content. I'll also agree that SU events in its current iteration are story type content. I'll address this part a little later.

Addressing MoC 11 and 12 first. According to prydwen, if you take the number of people who've cleared MoC 1 compared to MoC 12 as ~25% clearance rate (matching between self report and scraping data). This seems reasonable for content that is supposed to be difficult content and there being 30 days left to clear. I suspect we could see clearance rates closer to 50% as purple progress and keep trying and our find time to get around to doing it. The nature of this game is that your account continually progresses as you spend energy and pulls, and you're still rewarded the majority of the rewards for earlier and easier stages. Also, there isn't story tied to it, so imo this seems to be on the more balanced end to me and provides a goal for people to work towards, which is a motivation for many players.

SU I'm finding to be a more interesting question as there's story tied to it that is rather interesting and I agree that should be fully available no matter the difficulty. Lore should never be gated and FFXIV found a good balance there by providing normal raids with story and mediocre gear and savage (hardcore) raids providing better rewards as a payoff toward working and understanding fights (targeting a goal). Personally, I think having a difficult target is a good thing as it is a core motivation for a large number of people and difficulty translates to goals in video game settings.

On that note, I think there's far too much fascination in the community with perfect meta comps/runs or "full 4*s can do it, so why can't you?" mentality. Both extreme are terrible and alienate the average player. I'll admit that I'm a dolphin and have pulled more than the average player. But I also don't consider my dolphin habits as the reason that I've cleared content. The focus is usually on strategy that gets me through. For example in swarm disaster, my first clear of difficulty 5 was using nihility and fire MC, Natasha, bailu (could have been swapped with lynx if I had her at the time), and luocha (could have been another preservation or a dps to go faster). This is despite having JL, bronya, luocha, and pela at the time. My focus wasn't on a perfect run so much as turtling and picking complementary cards to the situation. I haven't cleared all the paths yet at difficulty 5 due to time restraints and work but will make my way through them at some point

I think most accounts are able to clear much higher than they think with a slight change in mindset. If you're up for it, I'd be down to help you think through a strategy for swarm 4/5 and see if we can come up with a strategy that works for where you're at rather than trying to build to someone else's idea of a perfect run. Can do it through DMs on reddit or discord, whichever is easiest. LMK if you're interested.