I have had no problems with Shopify itself and found it easy to use, great for CRM/order management/sales funnels, and handy as a POS for in-person events and b&m.
It is frustrating in its reliance on 3rd party apps, IMO, but I like being able to offer Amazon Pay and Log In with Amazon and to control my shipping options.
When I did try once to integrate Shopify with Amazon (translating Shopify listings to Amazon listings), it was a losing battle and category-dependent, but that was circa 2019, so it has perhaps improved since then. I have never tried to go from Amazon to Shopify.