The thing with Squarespace is that there is an option to do eCommerce stuff. It is good if it is not your primary or secondary activity. If you just need it to hang there and be available - it is appropriate. However, if eCommerce is a primary focus of your operation - you better think about transitioning ASAP.

However, it is better to compare your current platform with the other eCommerce platform.

Shopify is a good option because it is simple to operate. It is also not exactly cheap. You can go with WooCommerce. It is free but requires skills to make it going the right way.

IMHO, Magento is a better option for you. It is well-balanced, there are many fun tools and large community around it. UI is fine and you can easily do marketing stuff to promote your place.

If your focus is more so on the sale of products, Shopify is the most robust when it comes to its style, merchants options and tools/apps it provides for e-commerce. It’s easy to set up and maintain as well. Shopify is e-commerce first and other things like blogs and etc come second.

Squarespace is the other way around being that their initial focus was on a creating beautifully designed websites for bloggers, artist and etc. It’s only been in the past few years that they’ve offered tools for e-commerce. It’s better than it used to be however they still need some work.

I hope this is helpful :)