It isn't wrong. You could also say the fundamental reality is composed of English Peas and you wouldn't be wrong. But would it be useful? The usefulness of the label we apply to the "fundamental substance" depends in part upon how many steps we have to take to relate that label to everything else.
The dichotomy of Dualism vs. Monism:
For ages people have had the notion that this present reality is nested within another larger reality and this is the basis of dualism - the two realms: the earthly and the spiritual or the physical and the metaphysical. But there is an issue with this dualism. If the other realm is so completely different and separate from our own as to never interact with us then we might as well consider it to not exist. But if it does interact with our realm and if there is any regularity or pattern to the nature of this interaction then the interaction occurs according to some type of rules. And if the interaction follows regular rules then we can simply expand our definitions of the rules of this realm to include that realm. This means we can eventually expand our science and technology to make use of the rules encompassing both realms. At its core Materialism is really about the belief that reality follows rigid rules so if the "Spiritual realm" also follows rules, then it could in theory be folded under the tent of materialism.
Another way people have arrived at Monism as being the superior ontology is this: at some point we realize the definitions and boundaries are arbitrarily assigned based upon what is most useful in achieving a goal. Nothing exists independently but it always exists within a larger context. You could think of it as zoom level. We could theoretically zoom out forever and see everything as connected - one big thing. When we realize that boundaries are arbitrarily assigned or assigned by choice, then we start playing with boundaries around our own identities. Meditation and psychedelics and various other experiences can help us dissolve mentally imposed boundaries and see everything as One and this is often called the "oceanic" experience.
So it seems that Oneness is the ultimate reality, but we find our selves in a world where it isn't useful to focus on this most of the time, and we can't really talk about Oneness because words have definitions which are boundaries which break things up into pieces. Oneness is like the black hole at the center of being. We can use words and metaphors to orbit around it. We can see its effects, but we can't see it directly. If we stop talking/judging/using/desiring/acting, then we fall into it. Since it is the unification of all polarities then it is paradoxical and paradoxical metaphors are used to describe it. A shimmering darkness. An empty fullness. A humming silence. It is eternal life and ego death. etc.
This Oneness cannot be described. One of the ten commandments is to not make a graven image of it because to try to imagine it at all is to be deceived about what it is. But nevertheless we will make a graven image and try to talk about it.
Oneness alone is a completely useless concept. It is only useful when contrasted with our present apparent condition of separateness which often inspires love and compassion and it is also useful to dissolve mental stress contained within mental structures built of words and boundaries.
So the fundamental base reality is Oneness, which is completely useless to us because we can't talk or think about it. So we can assign any word to it and it will be correct. We can call it consciousness or mind or material or just "The Word" or "English Peas" or "Golden Calf".
As soon as we label the Oneness with a word, any word, then everything else is implied. As soon as you apply a word to it, then you have to define that word, and then you have to define the definition of the definition and then you have to define the definition of the definition and so on in infinite regress until the whole universe is described and everything is then composed of words.
How ironic that "Thou shalt not make any graven image..." was engraved upon stone and that those words themselves would be worshipped. And as Moses came down from the mountain he found they had made a golden calf to worship and so he threw down the stone tablets shattering them which is exactly what Words do to the Oneness. He made them grind up the golden calf to a powder and spread it over the water and made the people drink it. This is a representation through story of the black hole of Oneness and the inability to apply words or thought to it without the infinite regress fracturing everything and grinding the Oneness to powder which ultimately composes us.
So you can say "The fundamental reality is Consciousness" and that might be useful in some respects. You could say this is a dream within a dream or a simulation within a simulation. There's nothing wrong with it. But it causes a problem in other respects - for one because we can't talk without causing problems - but also because most people agree that consciousness exists on a spectrum of complexity and the further away we get from our level of consciousness (either up or down in complexity) the more difficult it is for us to relate to it and so it begins to lose its meaning. Also, the materialists have issues with this because consciousness is complex and in some ways mediated by and dependent upon material so how can something complex with prerequisites be the fundamental thing? Our understanding of consciousness also requires an object or context to be conscious of.
I think it is more useful to say that this paradox is true: Reality is fundamentally One and it is shattered into irreducible complexity. And any attempt to describe a fundamental substance of reality will be 100% accurate in some ways and it will fail in other ways, and so we can only do this in order to provide some kind of use in a limited context.
So my preferred label to apply to the fundamental substance is: PATTERN because it seems to provide the shortest most efficient definitional path to everything else. Pattern implies similarity/difference/choice. This is the fundamental Trinity. Since choice is required to set boundaries which compose the pattern, you can still consider this to be an expression of idealism. But since it is not called idealism and since it sounds objective and implies regularity or rules then it can appeal to the materialists who prefer regularity and solidity. Choice also implies a goal which implies a time lag between goal origination and goal fulfillment and also implies a frustration inherent in all creation and also implies power imbalances which result in everything from food chain to politics and evil.
