This question can also be applied to Carbonara. Is it a real Alfredo, or a cheap, easy, cheating Alfredo? On that note, what is the one ingredient you shouldn’t find in either a real Alfredo or Carbonara?
Looking around on the interwebz, the jury seems to be out on whether fettuccine Alfredo is a jin-you-wine Italian dish. Although Marcella Hazan provides a recipe in The Classic Italian Cookbook. Her recipe calls for parmesan and a touch of nutmeg. No parsley, no Romano. https://www.disgracesonthemenu.com/2012/02/italian-myths.html
Bacon and cream are not used in carbonara sauce. I've seen recipes calling for guanciale (cured pork cheek), which might be hard to find outside really hard core Italian neighborhoods. Other recipes call for pancetta. But bacon? NFW.
Bacon, preferably fatty and thick cut, can do for Carbonara in a pinch.....but you are right, it’s not the right ingredient.
What I was going for on both Alfredo and Carbonara is cream. Neither should have it. Not that I don’t use a little cream in an Alfredo on occasion, if I don’t have the proper butter (Plugra is my preferred).
That’s the problem with heavy cream in an Alfredo. An Alfredo made without cream is going to be rich (it’s just butter and cheese, after all) but it doesn’t have to be heavy.