For you, as the business owner, using Squarespace for your website is so much less work, so much less headache. You can actually focus on building your brand, and worry less about al the complex backend website technology. So from that stand point - Squarespace is superior to all other web platforms.
The downside, is that you cannot do tons of customization. Especially for Ecommerce. You get basically what Squarespace allows. In my opinion, if you don't have $20,000+ per year to spend on a Website like in WordPress or Shopify to keep it working and looking good - then Squarespace is a superior (and better) alternative.
All that extra money you save using Squarespace, you can use to do creative marketing, like inspiration Videos, or building a great Customer Experience, or focusing on Testimonials, or improving your products and services. There are all sorts of ways that good Marketing does so much more than just having lots of custom coding which ends up just being a distraction for you - the business owner.
Most business owners have someone tell them something like this:
"In order to get a good website you have to use WordPress"
That is such a lie. You need to focus on building your business. Not website technology. Focus on your process, your customer services, your products, your employees. Make a great company. Let the website just be 1 tool in your sales process. But it is not the only marketing tool you need.
So you need to clear your mind from all the distractions that complex website technologies cause. Focus on building your business. And let your website be beautiful, simple and stress-free.