It's very use and location dependent. I'm going to get a good or at least relatively good dining room table. Some cubbyholes/shelves for a closet? IKEA is fine. I also have an IKEA bureau in my bedroom. I occasionally wonder if I should have splurged on a "real" piece of furniture but it saved me thousands of dollars and is perfectly adequate.
I have an IKEA LANDSKRONA (in Gunnared dark grey) and it's a good sofa for like 650 €. I don't think I've really considered sofas to be that markedly better than mine even if they're double or quadruple the cost.
IKEA is ideal for a certain stage of your life. It's ideal for optimizing vertical space. It's largely function over form. It looks like middle school classroom furniture. And when junior writes on it w/ a sharpie ¯\_(ツ)_/¯.
When you have the space for a separate dining room, agreed that used antiques are comparable in price.
I wouldn't touch their couches rich or poor though; they're painful.