If Shopify traffic has plateaued for months, outsourcing SEO may help - but...
https://iris-wiki.win/index.php/What_Happens_If_SEO_Work_Does_Not_Move_the_Needle_for_a_Month%3F
If Shopify traffic has plateaued for months, outsourcing SEO may help - but only if the work fits the bottleneck. Ask for Search Console non-branded traffic, a clear diagnosis, and what changes they will own - not promises.