okay, let me dissect this a little ? Expect that I never do this except under expensive chintz, and then only if color shows through. Kim in Oregon may be a better person to ask this question of.
what were your expectations ? See if you can name them for yourself.
Slipcovers at best are clothing. They are never, and can never be skin. A skin like appearance is lucky, and still it will slip ( like cat's skin ).
Your best disguise is still a dull surface, woven pattern, a print that contains colors with vivid contrast or just enough swirling contrast that creates movement. Bulk or stiffness, and then hot or white color, but not receding colors, especially if lacking any of the other qualities.
If you padded up a piece of furniture the best way you could, which still isn't upholstery, but the most time you could possibly devote, if the fabric didn't have help from the list above, it would still not appear to be skin like. Even then, it's cats skin. It's only as nice and perfect as it was recently tucked in.
Lining at best will only help to disguise a vivid pattern on the upholstery if poking it's head through a too thin a and too light colored slipcover fabric. At best, it's a slip, think the thing you wear under the dress you don't own.
You can never disguise enough with lining and padding alone, button tuft depressions, so well that you will forget they are there. Forget is a good word here, if it bugs you, it will continue to bug you, unless you choose to forget it.
I accept pretty easy, the boogers that go with ownership of the fresh cover of my choosing that goes on the furniture I happen to own. This is key, I can choose fresh fabric, the chair or sofa is what it is. Lumpy, dumpy, and bumpy never goes away. Wholey arms and crooked cushions only get a little better with padding out.
Lining at best is white out, helping my fabric choice cover COLOR better. The chair or sofa may still be as lumpy as it ever was, if not to my eye, certainly in my memory. It will now also shift like cats skin, but worse, there's two layers to shift, if a garment was made. Staple it on for less shifting.
Now major makeovers, I leave to my upholsterer. People who consistently choose white slips or expensive chinzt should do this, reupholster in muslin. I make clothing, I don't do cosmetic surgery. That's just me. Where there's a budget for cosmetic surgery, heck, take the money, and practice.