> Humans have a larger neocortex compared to other mammals, which gives them more storage, working memory, and computational potential than other animals.

Computational cognition models are more and more replaced by embodied cognition models. Not only that, "computation-like" functions of human consciousness is by far not limited to the neocortex. Much older parts like cerebellum play a significant role in noise filtering for example. Just like we have adapted our tongues to a new purpose of speaking, we have been adapting the existing information processing machinery to perform higher level cognitive functions. Neocortex is not the add-on consciousness chip.

> The curses of the human condition are anxiety and regret, the conditions that render people unable to engage in the present moment.

I will object to this on the basis of being an overly romantic notion. The preoccupation with future and past is simply requirements for the predictive processing we have to do in order to have any agency in the world. Normally this is fantastically adaptive, and a requirement to fulfill our needs, which I presume is required for what you call happiness. (Not to mention this is not even a human-specific trait). Being genuinely stuck in past or future is the disease state of this otherwise adaptive feature, and because it is an emergent property of a complex adaptive system, it is harder get out of it because it resists that shift.

Which is why one trick interventions like "be in the present" moment are likely to fail to get one out of those states in isolation.

> What characterises flow state and mindfulness is total absorption in the present moment.

We need to expand several notions here. Being in present moment is such a vague metaphor that it barely describes anything. A more apt description would be being in perfect conformity and harmony with the task at hand, being able to dance with it, being able to adapt to the challenges it throws at us. And it brings different criteria for flow state vs mindfulness; in flow state there is usually a sense of dissolving ego boundaries, there is a sense of being one with the task itself. E.g rock climbing. Mindfulness is a more complicated state, because the task at hand is tightly related to the metacognitive state of the person. There is usually much more ego awareness, because the focus is the ego content. The eventual aim is to gain flexibility over the ego content, and being able to shift the opacity of it (i.e. swiftly switching between thinking from "i am thinking this" to actually thinking it, and during that process more fluidly change the "it"). As such, I would agree animals could be in something that resembles the flow state, but can't really do mindfulness.

> The dog and the cat and the cow and the horse, given physical comfort, do not seem to worry about the future or regret the past.

I again find this to be an overly romantic notion. Just like I've mentioned, animals do have a capacity for learning, because it is adaptive to be able to undertake predictive processing. Which makes way to the "worry"s you mention. If you spend time with any animal that has PTSD, you'll immediately realize that they are stuck in a state of predicting harm that doesn't exit. That is an expensive, low precision state and not one of comfort. They can be trained out of their traumas, sometimes more easily than with humans, but they also can't do any of the rational/cognitive interventions that we could do.

Basically you're advocating for a lower state of consciousness because our cognitive machinery can fail more drastically than other animals. I would agree with the second part, but not the first part. We have been developing a plethora of techniques to upkeep our psyches, mindfulness training being one (and remember one intervention alone can't do much with complex adaptive systems), we've been just not good at scaling the know-how over time and people, at least not in comparison to our default state of ignorance.