Hi, I'm a web developer with 10+ years exeprience. A friend of mine that uses shopify beleives that there is not really an effective way to use product custom attributes with shopify.
Do other shoify merchants feel that there is still some limitatoins, potentially ones which could be addressed with an app?
I hope you are referring to the product attributes.
Actually shopify provides metafield which can be used to save custom attributes of products, varients, blogs, articles, collections etc.
There are different apps which provide the feature.
https://apps.shopify.com/metafields-editor - Free with limited feature
https://apps.shopify.com/custom-fields-2 - Paid (Good option)