According to your account, Vedanta claims that the world is an illusion and that only the Brahman is real.
If the world is an illusion, Vedanta has to deny the reality of the world. To it, in the way you construe Vedanta, the world is the empty set. That is to say, all experiences are on par because they are all illusions. One cannot distinguish between experiences unless one introduces the notion of a differentiated reality. From this, it follows that a vedantin should not be able to discriminate, say, between the following: the pain you have by stubbing your toe, the pain you have when your arm is cut off without anaesthesia, and the pain you feel when your loved one dies. If he does draw a distinction between them, he is distinguishing one illusion from the other and the only way of doing that is to ascribe to these illusions the status of reality: this is ’less illusory’ than… this is ‘more real’ than… this ‘pains more than’… this pain is ‘different from’…and so on. If he does not distinguish, and insists there is no difference between falling in a lake and bumping his head against a tree, who would take him seriously? Do you believe that Indians are such cretins that they would simply accept such inane stories? Surely, if ‘Brahman’ is all there is to Vedanta, all vedantins must be perfect imbeciles. In that case, we do not need heavy-duty tantric stuff to shoot them down; a simple dose of commonsense will do.
Shankara was a vedantin, as you know. If you had glanced at his writings, say his Mayapanchakam for example, you would have known that what you say does not make sense. In this poem, he describes the power of maya and ascribes agency to ‘her’. He speaks about those whom she spellbinds: they are a plurality of creatures including the learned, the human, the animal, and, of course, the Brahman. How could he talk about the ‘power’ of maya, her incredible abilities to control creatures, if both maya and the plurality of these creatures and their experiences were not real? Maya makes sense only if the world and its richness are real. Maya does not imply the absence of the experiential world but presupposes its reality instead. To say that maya is the nature of reality makes sense. It is, however, linguistic nonsense to say that illusion is the nature of reality. How could the vedantins discuss with each other if they spouted semantic nonsense?
It is obvious where the problem is to be partially located. You translate ‘maya’ as ‘illusion’. This translation does not work, when you are talking about one of the central categories that many Indian traditions use. To understand why it could not be a translation of maya, consider the following argument. After all, Vedanta claims that when one realises the unity of “oneself” and the “Brahman”, one achieves enlightenment. If ’everyone’, except the enlightened, is under the sway of ‘illusion’, what causes it? Vedanta claims there are causes. If there are causes, they cannot be ‘illusionary’ entities. If causes are real, so are their effects. ‘Illusion’ is an effect. Therefore, ‘illusion’ is also ‘real’. In that case, Vedanta would become flatly nonsensical. Whatever else Vedanta is, it is not semantic nonsense. Surely, one should understand what Vedanta denies and what it does not, before indulging in silly contrasts.