Zen browser is my daily browser since many months now.
Most of your fair criticisms I have solved with Zen Mods and playing around in the settings.
The Widewine limitation is really why I will always keep another browser to fall back to: I recently discovered that all of Udemy is non-playable in Zen.
I've started using more Zen Mods recently too, the most important one I would say is Zen Context Menu - which lets you de-clutter the options when you right click anything. There are way too many options being shown when you right clicked the sidebar, but it's a lot nicer to use now.