I found Shopify as a great SEO enabled platform and easy to run an online store. You can easily optimize all of your categories pages as well as product pages.
Your website seems SEO optimized (on-page), except well optimized Meta Tags. I would recommend to have 50-60 words Meta Title which includes your targeted keyword. Also backling is the best practices to improve you keywords ranking.
I have the same experience with you. But SEO on-page is depending the theme that you are using for your store. So when you choose a theme, you should check demo first.
Secondly, there are a lot Shopify app that isn't friendly for SEO. You should carefully before install. Ignore the app that slow, break your on-page etc...
Hi, As i am running an ecommerce store i didn't get or face any issue regarding eCommerce SEO from their codding but yes there might be some issue may generate if you are using any unauthorized or low popular apps so it is better to take some popular apps which are mentioned @App Store: Ecommerce App Marketplace by Shopify & Best Shopify Apps for Your E-Store in 2017 - Withintheflow because some time html error or bugs accrue when they update their apps features and it can be effect your website growth.