Pop tarts are also a bastardization of some other more traditional food but I don't know which right now.
If you look at how they apply the icing you can clearly see how they started putting less and less on each pop tart. I don’t buy these things because I want to eat the crust!
Then, on a more recent whim, I bought some store branded toaster pastries from my local grocery store, and they were exactly the Pop Tarts I remembered.
They're also producing products in almost every aisle of the supermarket and gain an economy of scale on things like only needing a single one of eg house style for every product.
There certainly wasn't anything at the scale of Walmart, Aldi, Kroger, or Publix these days.
Consequently, it was easier for General Mills et al. to use economies of scale to sell quality, profitable products.
Now, it's the grocery stores that can do that.