Standard has a number of options for card draw. Glimmer of Genius tends to be the most powerful as an instant-speed way to see up to four cards, but there are also cheaper options in Supreme Will/Anticipate, Opt, and Chart a Course. Hieroglyphic Illumination has seen some play, but it tends to be in decks that focus on cycling.
In Modern, there are even more options available. Tempo is important and waiting until you have a bunch of mana in play to start drawing cards isn’t always realistic. Serum Visions tends to be the most cast of the bunch, but we also see Sleight of Hand, Ancestral Vision, and a lot more Opts cast in Modern than in Standard.
But Ben Stark thinks that Modern is ready for Hieroglyphic Illumination to make the cut.
The slot that Illumination would take is Opt’s, so that’s the card that we should be comparing it to first. They’re both effectively instants for a single blue that draw a card, but Opt gives you a scry first. This means that you get to see slightly more cards, but it’s not drastic. It makes it slightly easier, as well, to set up a Terminus, but Opt isn’t exactly amazing at that either. Opt is much weaker against Chalice of the Void decks since they tend to put Chalice on 1, but this shouldn’t be a determining factor.
The biggest downside, in my eyes, to playing Hieroglyphic Illumination over Opt is that you lose that synergy with Snapcaster Mage. Being able to hold up 3 mana to Snap back an Opt as a flash Silvergill Adept is something control players have been enjoying quite a bit in Modern lately. That said, Ben Stark argues that Snapcaster Mage might not even belong in control decks in Modern these days either!
The argument over whether Snapcaster is worth a slot or not is for another day, and likely for Ben to argue the other side of, but it’s not crazy. With Teferi, Hero of Dominaria as a win condition, you no longer need the incidental damage of Snapcaster Mage, and the small amount of card advantage provided by a 2/1 flash creature for 2 isn’t worth all that much. Snapcaster is still a quality card, but it’s not insane to cut it.
Once we don’t have Snapcaster Mage in our deck, it becomes perhaps even more clear cut. Hieroglyphic Illumination doesn’t have the ability to scry, but there are a lot of matchups in Modern where you want to turn your Opt into a draw two for 4 mana if given the chance, so having that “split card” option is really useful. Modern features a high power level, especially in discard spells, and there are many matchups where the games go long. Having the ability to turn your 1-mana draw spell into a clunkier draw-two when you have the time is quite nice.