I agree that Magento 2 continues to target mid-market and enterprise users while leaving many SMB's behind. I've seen a lot of small B2C retailers that only need basic functionality move to SaaS products like BigCommerce and Shopify. Many of these small businesses struggled to keep their Magento sites patched and properly hosted. They could have stuck open-source with something simpler like WooCommerce, but for $29+ a month, SaaS makes sense. As they grow, it's foreseeable that some will shift back to Magento and other open-source platforms.
In the open-source world, beyond WooCommerce which is more SMB focused, I'm starting to see growing interest in Shopware. It's popular in the EU. With folks from the Magento community like Ben Marks getting involved, I expect to see it more and more.
However, I still see lots of SMB merchants choosing to double-down on Magento Open Source (aka. Community Edition), and new merchants choosing it. It's still the strongest all-around option in open source eCommerce in key markets like the USA.
I will concede that SMB is a large category. According to Gartner, it includes businesses bringing in up to $50 million in annual revenue. The merchants that are now aligning with Magento are into the millions of $USD in annual revenue.
I'm also not convinced that Adobe is "killing off" Magento Open Source. Keep in mind that Adobe just released Page Builder for Magento Open Source users: https://magento.com/blog/magento-news/bringing-page-builder-content-authoring-magento-open-source-co...
It now takes more resources to maintain a Magento site when compared with the days of Magento 1, but with SaaS products coming of age, I suspect that, even if M2 was less of a beast, a large percentage of small businesses still would have shifted to SaaS solutions.
