"No Multi-Process Architecture" This is a feature, and I like it. The rest is just flamebait.
And there is a simple solution to that (poor multi-core utilization): go back to a one-window, one process model (go back, as in delete a lot of unnecessary code); forget the browser tabs - let the OS handle multitasking and let the window manager handle the windows.
This also ignores the other important benefit of mparch: sandboxing. The browser needs some elevated access but the page content does not.