On Following Recipes

You know when your level of expertise has reached the point where you don't cleave slavishly to every little detail in a printed recipe. Half a teaspoon means "more or less," and you let your tastebuds be the judge. You know that you can get pretty much the intended flavor of, say, onion and garlic, by using a handful of shallots instead. You even know when you can introduce your own ideas of ingredients, such as adding some toasted walnuts to a cookie recipe. You might be more creative, and use just the formula of a recipe, the "how-to" — I do this with one of Deborah Madison's recipes for savory bread pudding — but make the dish with entirely different flavors.
You might know, just by reading it, that a recipe is going to be dead wrong, and you'd better not attempt it at all. Experience will have taught you, for instance, the best time and temperature for a piecrust, and when you come across a recipe that's seriously off, alarm bells ring.
I feel I have about that level of expertise. I'm not a serious baker, and I consider baking more of a science than an art, so I usually follow baking directions pretty carefully. I'm an avid soup-maker, though, and seldom follow strict recipes for soup. I get the basic idea, and then I take off from there.
So I was excited to see a recipe in this month's Saveur for Soupe d'Herbes Potagères ("Pot Herb" Soup). It called for potatoes, a leek, some onion, a lot of parsley, some heavy cream and various fresh herbs — all of which I just happened to have on hand (and almost always happen to have on hand). Plus, the picture was gorgeous: a velvety greenish-khaki colored puree that looked homey and comforting and oh, I could almost smell it.
I regarded this recipe as a suggestion, and yet I actually followed the directions fairly closely. I didn't measure strictly, because I didn't feel I needed to. I didn't time the cooking exactly, because I know when something's cooked enough. How bad could that be?
Now, I realize that the recipe called specifically for russet potatoes. And I realize that the potatoes I had on hand were (I think!) Yukon Golds — beloved Cranky Husband is the potato buyer in this house, and that's what he usually gets. But I've been led to believe — and experience has reinforced my belief — that a Yukon Gold is pretty much a good substitute for a russet. (Let the horrified comments to the contrary now flood my inbox.) I've baked YGs, I've roasted them in oil, I've boiled them, I've mashed them, and (I think!) I've used them in soup.
But I got goop.
Neon green goop.
Gluey, vivid, unsubtle, nearly tasteless, non-comforting gloop.