Hyde here from Shopify.
I'm sorry to hear that you feel Shopify does not meet your customization needs! Are you aware that we've started rolling out our Online Store 2.0?
If not, I'd highly recommend that you check it out before deciding to swap platforms. This is because we've ramped up our theme editor considerably in line with Shopify's mission to make commerce better for everyone.
If you're still certain you want to switch to Squarespace while using Shopify's Buy Button, then you'll want to follow our Shopify Buy Button guide. Of course, you'll need to check that Squarespace will tolerate Shopify's Buy Button being embedded in its coding too!
On Shopify's side, you will be able to downgrade your plan from the Shopify Basic Plan you're currently on at $29 to the Shopify Lite Plan at $9 in which you lose the Online Store but can continue to use the store admin.
Was there something in particular that you felt was missing? I'd love to get your feedback to pass on to our developers so that we can continue to improve our product offering!
All the best, Hyde.
That's great to hear! You'll be pleased to know that Online 2.0 gives you the same flexibility when customizing your pages that you had with the homepage.
You can upgrade to Online Store 2.0 in several ways:
Of course, don't forget these considerations when updating your theme. I hope this all helps! -Hyde