Please give an example of how this would happen. How would you "recreate" another spell using silent illusion? Keep in mind that silent illusion is automatically revealed by physical contact and can't move except when the caster uses an action to move it; an illusory blindfold over a creature's eyes would fail on multiple fronts (first because the creature is in contact with the blindfold, and second because the creature could take a single step and the blindfold would no longer be over its eyes).
I was mostly referring to copycat effect of light spells (if illusion can create light), invisibility effects (if illusion can remove/bend/reflect light), and darkness shenanigans (if illusion can block/absorb light). I'm not saying you advocated any of those, but that's why I think one should be careful about allowing illusions to create, block or reflect light.
But again, as Ovinomancer said, illusions as described in D&D (and fantasy in general) are irreconcilable with real-world physics. Something's got to give. In the face of this paradox, we've got to accept that illusions won't logically work or be rationally explainable, and go with the same willing suspension of disbelief that we are capable of for many other aspects of the game.
In order to be visible in the real-world, an object as to a) emit in the visible spectrum, or b) reflect the ambient light toward the onlooker (assuming there is ambient light in the first place).
Illusions are magical constructs that can make something visible and look real enough to fool anyone that doesn't physically interact with it, but that doesn't really exist. So far in this tread, it has been theorized that...
- Illusions don't create, absorb or reflect light in any logical ways: it just make the illusory item visible and indiscernible from a real one, because magic.
- Illusions block light and reflect it back to it onlooker (the reason we see them) but don't interact with the physical world in any ways, because magic.
- Illusions don't exist as a phenomenon but as a figment of the imagination of the onlooker. The illusionist therefore doesn't mess with our senses as mush as it messes with our mind. And this figment is the same for everyone, because magic.
Personally, I don't think one explanation is more valid than any other - all require that we ignore the laws of physics as we know them. However, I find that the first one is the simplest to explain and to implement within the RaW parameters of the spell without too much surprises and dubious shenanigans. And yet it remains a very powerful tool in the hand of a clever illusionist.