As with anything else, it depends on the WalMart what fabrics they have. Some are better than others as far as selection and quality goes, both in the fabric department and in the ready made clothing they offer.
Just an isn't it ironic note on this...the one with the really nice clothing lines that ours does not offer, has no fabric and very little craft stuff of any kind, while ours has a fairly large fabric section, as well as a large craft section, but not as much variety in the clothing section.
And the WalMart about 30-45 miles north has different fabric selections and additional fat quarters that are better quality than the ones on the other side of the fabric department. Plus they have a big what I'd call fabric bonanza in the spring with extra tables set up and all sorts of bargain fabric. I bought 10 bolts of fleece at $3 a yard last year...the really nice stuff that is almost double weight.
No matter where you shop, you have to know what you're looking for.
And just a note on antique quilts...many of them were made with whatever was at hand, not all of it even in a single quilt being of the same quality.