Falling 2, or even 1 release behind makes maintenance a nightmare.

I also explain to people that even though WP and WC are free, and very easy to install/setup, you're essentially running your own ecommerce software platform, and are on the hook for maintenance and any problems (security/scaling etc.) whereas hosted platforms like Shopify take a lot of that off your plate.

Because as questionable as it may be resources wise, well it compares pretty well to the likes of OpenCart or OS Commerce, and significantly better than other WordPress shop plugins I've seen in the past (like Shopp). At least you can take your WordPress development knowledge and apply it to templates/plugins, have some decent documentation lying around to fall back on, and don't have plugin developers trying to nickle and dime you for every little thing.

There's probably a market in there somewhere, if someone wanted to actually create a decent ecommerce system that doesn't require a ton of resources, doesn't rely on another system to function and whose community actually knows what the hell they're doing.

I've seen many customers struggle with it and move to Hybris or Magento.

Hybris has a very good comprehensive and stable and extendable ecommerce solution. The only downside is its from SAP and not open source, which might not be bad for a medium sized to big ecommerce shop.