Let's be honest, Spagetti Carbonara is hard recipe but it's totally worth to learn it. This recipe is respecting the original procedure so no cream, there is no discussion about this! Same applies to cheese, originally it's done with Pecorino Romano which is sheep cheese, can be done with other types like Parmigiano Reggiano or Grana Padano but it changes the taste of the dish significantly. Garlic is also not supposed to be in the original version, however even some high profile Italian chefs are using garlic in their recipe, it gives more complexity to the dish, i prefer it too.
If your sauce is very liquid from excess pasta water, or there was too much egg white. Turn on gas on the low / or just use still hot stove plate, be gentle with heat. Mix intensively until it thickens up. If you stop steering the eggs in the sauce will cook, so make sure to keep it always dancing.