This is personally where I think their intended stress is going to be for normal content. Pacing is easily enough adaptable and can keep the fight engaging for anyone without necessarily compromising on making the content too difficult as to potentially stonewall people or change the target audience entirely. Can't speak on beyond that, isn't my place. But the original comments were about stress, and that stress takes on a variety of forms aside from "just ramp up the difficulty" - Which Yoshida commented on at the time. I think if they want to step up the difficulty of that entry content, then they really ought to be spending a lot of time nurturing the content that has had its teeth lost to time, e.g., ARR > SB content.
This final part of yours I think is spot on. This is the intended audience. Easily accessible to most skill levels, and frankly anyone that tries to pay attention, but still has the risk of wiping people. I still have healers and such getting taken down by final boss on level 95 dungeon and final boss of level 91 dungeon. Just as I have seen people get baited by the Cross AoEs and circular AoEs on the first dungeon of Alexandria. There is still some legitimate threat to a casual or lower-skilled player. Personally, I'm a casual player by nearly every stretch of the definition (outside of DoH/L), most dungeons I found easy but required some level of engagement or paying attention, e.g., the order of AoEs in Alexandria, or positioning myself to not get crushed by unfortunate positioning on the Level 91 boss (I've absolutely seen people essentially do themselves in because of their position alone). But even these things are just things that people don't pay attention to when actually doing the dungeon. Some will treat it as reactionary, and just react to the bosses, but some will treat it as more of a dance and will know the sequence, and I think something like this is a mentality thing, and when you have that mentality it's not really easier to create that desired difficulty/swing without changing the target audience for that content entirely.