I had a roommate once who was an okay plain cook - he'd saute meat and vegetables, boil vegetables, cook potatoes, and so on. One day he asked me for a recipe for a cake, as he wanted to take one to a potluck.
I dug up a very simple one bowl cake recipe - no beating the egg whites, or mixing things separately. Then I went out to run errands. When I came back I found out that he had been out of milk - so he used yoghurt. That was kind of sour, so he added mashed bananas. And there may have been one or two other things. What he got out of the oven was not, technically, cake, it was more of a sour baked custard.
I also find the ratings on on-line recipes amusing, but I do understand the comments. When I look at on-line recipes I almost never follow them exactly. I'm generally looking for the general ingredients and amounts for a dish, and then I wing it from there. Quite often I *have* to improvise based on the availability of ingredients. For example, I can get whole milk and whipping cream but nothing in between, and the brown sugar is a different texture and taste than what I grew up with, and I can easily find walnuts and cashews, but not hazelnuts or pecans.
I've occasionally explained to people that baking is much more like chemistry than ordinary cooking. You can substitute in some cases, but you need to know what effect it will have not just on taste, but the chemical reactions.