1st of all, tiling managers are a matter of personal preference, no wether it's "broken".
2nd of all, I've used i3 plenty, and the amount of power it gives me when I'm working is immense. I no longer need to alt+tab 7 times to get to the terminal for the monitoring servers, I always know they're on screen 4. I need my web browser ? I know it's in screen 2. Heck, I can pin apps, and even screens to specific monitors. When I'm working on an incident, my throughput is basically multiplied by 3 as a result of how streamlined my work environment is.
That is simply not possible with other environment where the mouse is the main device. Yes you have virtual desktops, but try having 15 open terminals without having them pinned in some form. Just a simple swipe to the corner and your GPU will heat-up from the 3D acceleration required to show all the windows :D
All-in-all, I genuinely believe that tiling wms are an amazing godsend, but for my use case. And I cannot emphasize this enough. It's a personal preference. Yes it's a bit of a pain to set up (although I literally used a two-part youtube video to set up i3, and never touched it again, not even need the Arch wiki), but if you don't have to tinker in your configuration are you really running linux :D