I am the sole front end developer at ReportDash, an online report and dashboard builder. We use backbone, backbone layout manager & coffee script and never ever once regretted the choice. The code is highly organised, thanks to the structure provided by backbone layout manager, and is pretty much readable and extensible. And not even once I felt limited by the framework.

The code has got quite complex over time, and I strongly suspect I would have gone mad if I had used a different framework. I used to wonder why the hype over react, vue, angular etc.