The easiest platforms are SaaS-based – they act like LEGO (Shopify or inSales). Easy and cheap, but no customization.
The most common option – CMS development. They are modular, and the modules of many of them are collected in sets (or editions) designed for certain types of sites.
The most potent option is framework-built platforms. The need for serious programming costs makes the development more expensive, but the result is also more individualized.