Sounds more like they picked the wrong tool for the job. SourceGraph doesn't really need a heavy front end framework because it is not an SPA and have a very small portion of interactive content on the page to begin with. Also what they complained about is mostly not specific to Angular, but has to do with SPA front-end dev in general. The title feels like a bait and switch.
The original post's disqus can't be loaded, so I'm posting it here: I have noticed that Gulp's watch task's time reporting is a bit misleading. For an async Gulp task to be accurately timed, you need to either take a callback argument or return a stream/promise. When you do none of these, the task is considered done the moment it's returned, resulting in the microseconds time reported during watch - it is not how long it actually took to finish the task.
Why not use Component? It provides both package and file based modularization, has a builder, comes with GitHub-based package management and has an ecosystem already.