The shutdown isn't a complete shock. Blocks unveiled its modular watch project back in 2014, and it blew past its May 2016 release target as it tweaked the design to reach a quality level it would accept. Even by the standards of major tech companies, this was ambitious. Blocks not only had to design the watch and multiple modules, but write a custom operating system (using Android underpinnings) to support the technology. It needed a mountain of resources and time that it simply didn't have.
This is unfortunately an all-too-familiar tune. Modular mobile devices have long struggled to reach the market -- even Google axed its modular smartphone efforts in a bid to streamline its hardware strategy. The hardware has long faced technical hurdles (such as ensuring compatibility), and that isn't even including the challenge of finding partners to create a module ecosystem. Like it or not, it could be a long time before there's a mainstream smartwatch with more than a token nod to expansion and swappable parts.