I mean the replacement of Platonic/Aristotelian realism with the new "mechanistic" philosophy, the focus on the here-and-now at the expense of more otherworldly concerns, and the epistemological individualism and scepticism of authorities.
Conflating Platonic and Aristotelian ideas is really not a good idea. Metaphysically, Plato was the one with the "otherworldly" interpretation (namely that our world is merely a shadow of a more 'real' World of Forms/Ideas). Aristotle argued that our world was the real one. See also: the
problem of Universals, for instance.
During the middle ages, Aristotle was widely embraced by the Catholic Church. Thomas Aquinas didn't get his ideas out of thin air, and make no mistake: his ideas were one of the precursors to the Enlightenment. This shaped Catholic doctrine (which was, in a philosophical sense, far more complex and intellectual than those talking about "the dark ages" like to believe). See the
School of Salamanca, which advocated natural law and human rights, as well as responsible government and the sort of free trade economics closely associated with Enlightenment thought.
Sure there were ideas in ancient and mediaeval philosophy which were retained or reinvented during the Enlightenment, but the overall tenor of philosophy before the 17th century was much more otherworldly and less individualistic than it was afterwards. There was nothing about Greek and Roman philosophy which made the Enlightenment the inevitable result of studying it.
There are no inevitabilities, really. But there are probabilities. There was much in classical thought that could serve as a basis for further reflection and innovation, and
did. And not just once. Thomas Aquinas wasn't the only guy coming up with the type of ideas that he did. See also: Hugo de Groot (Grotius), Desiderius Erasmus and Dirck Volkertsz. Coornhert in the Netherlands. Utterly separate, influenced by Protestantism instead of Catholic doctrine, but still re-interpreting many of the same sources. Which led to similar philosophical and moral conclusions.
And then you get Descartes, Spinoza, Locke, Bacon, Newton etc. etc. They didn't get their ideas from a single source that you can just remove. They studied the classics, as well as the aforementioned thinkers (and many others like them, which I have not mentioned by name). They didn't suddenly come up with notions of individualism, empiricism and stuff like "the right to revolution against tyrants".
Many of those ideas were previously explored, if in a cursory fashion, by men such as Aquinas, Grotius, Erasmus, Coornhert and the great thinkers of the Salamancan School. The development was gradual, and what we call "Enlightenment" was not a sudden thing. It was a tipping point, when such ideas really became "mainstream" in intellectual circles... but that was a matter of time.
You can't just "erase" men like Descartes, Spinoza, Locke, Bacon, Newton etc. without first erasing men like Aquinas, Grotius, Erasmus, Coornhert etc. And to erase men like those, you need to get rid of the ideas and sources on which they based themselves: the philosophy, science and corpus of law of the Classical world.
Sure, you can delay the Enlightenment, and the earlier you start changing the TL, the more effective you will be at it. But to
prevent it? You'd need to prevent so much that came before and led up to it....