I agree! It's not the source of the fabric, but the fabric itself, that makes a difference. I am convinced that you can get high quality fabric in many more places than just expensive LQS and online stores.
If I like the fabric, it goes in my quilts. Most of my stash I have no idea at this point where it came from.

As long as you can tell quality you can shop anywhere. Quality varies everywhere. Joanns just makes it convenient and you never have to pay full price with coupons. I got a whole Christmas quilt backing and all for like 60 bucks so can you find a LQS for that price no. I also do a lot of small projects with joanns. Most big projects come from LQS but I have found lovely fabrics at joanns and their premium legacy muslin can't be beat it is wonderful quality

It's been the same with me. I bought a designer branded fabric from another source that wasn't a Big Box store. Once I brought it home & washed it as my habit, it is just as limp and cheesy as the reputed Big Box offerings.

I am now auditioning future fabric choices by running them through a simple test. Instead of buying a large amount of a given fabric, I make my selection of a given bolt. Then I ask for a sample (a small swatch) of that fabric. Or if swatches are not allowed, then I buy a 1/4 yard or so. I take that piece home & wash & dry it. If it's quality is up to my expectations, I go back & buy it. If not, I did not waste any money and time on hidden trash.

Although, if it's on sale or clearance, I judge it solely on it's hand qualities & take a chance!

I have found less than quality at quilt stores and great quality at Walmart and JoAnns. The key is to look at the quality and make your choices based on good quality. I do mix them all the time and have never found a problem. I love both purchases and use them all the time. Make your own choices.