While it is true that there are handcrafted items available on Etsy that wouldn't make it past a craft show jury, there are a lot of quality handcraft items as well.
I am an Etsy buyer and seller, and love the platform. I have also had good experiences using their alchemy feature.
As for determining quality of items that I have chosen to purchase on Etsy, I rely heavily on a combination of things:
1) Photos - Give a full view of your product, with good lighting in a setting that doesn't distract from the product. Add close-up photos to show detail work.
2) Good product description - Include materials used, measurements of the product, etc. I particularly enjoy the descriptions that have stories included and have printed those to include with items I have purchased as gifts.
3) Feedback - I look for good feedback on a seller's profile.
4) Good communication - During the sales process, I prefer working with sellers who let me know they've received the purchase request, andn follow-up when it's been sent. Some even follow-up a third time after they've received delivery confirmation to thank me for the sale and encourage feedback.
Be sure to check out the sellers forums on Etsy as there is it includes a lot of great advice on how to promote your Etsy store, stage professional photos, write clear product descriptions, etc.