Light of Promise effectively doubles Trelasarras growth effect, or can be put onto another creature to build a secondary threat
I also think it helps in the sense that Izzet doesn't always get a lot of great counter spells specifically in its color combo
Then there are non-basic lands that will give you specific numbers, such as mizzium blast furnace which gives you two red each time you tap it
Paying one to get a bit of card selection isnt great, and neither is paying 3 to kill something and give its controller a 3/3
In July 2025, a Gem Mint Blastoise was sold via eBay for about $88,000
Izzet spellslingers are a dime a dozen, and while the payoff here is Roothas ability to turn those into big Elemental creatures, this means the early game features relatively minor gains