Karo syrup in caramels

All corn syrups are not High
Fructose. The Karo syrup bottle asserts that it does not contain any HFCS . A little Karo syrup is used to keep the sugar from crystallizing.

The invert sugar helps to prevent crystallization. If all you have are sucrose molecules they want to bind into a crystals. If you add fructose and/or glucose to the party the molecules interfere with the formation of the sucrose matrix. You can make your own invert sugar (i.e. sucrose that has been broken into fructose and glucose), but that would certainly not simplify the recipe. I add some cream of tartar (which causes some sucrose breakage) to my caramels and use a lesser amount of corn syrup than many recipes call for, which has worked well for me.

Because I have terrible reactions to high fructose corn syrup (which is in Karo), I never use it. Instead, I make my own sugar syrup, which I keep jarred in the fridge. It's easy and inexpensive. and no HFCS. Other alternatives are Lyle's Golden Syrup and /or Steen's Cane Syrup.

I would follow the recipe. Corn syrup will help with the chewy texture. There may be recipes out there that don't call for it. It would be better to find a new recipe or you may end up with grainy caramels.

Corn syrup is an invert sugar, meaning that it in solution and remains that way. It does so because it contains a small amount of acid which prevents sugar molecules from recrystallizing. It brings that same property to mixtures to which it is added, such as your caramel. You could replace it with an equal amount of honey.