I'm familiar with 3d software suites, and they're (mostly) all highly-configurable, permitting custom layouts, panels, toolbars, and even enabling intermediate users to create UI tools.
To your point, they're also ferociously complicated for novices.
Bloomberg is a funny example. It's a well-indexed reference, rather than an expressive tool, so mastering its shortcut-dense interface is an affordable cost to professionals of modest technical sophistication.
I wonder if TurboTax is in the running; for all its blandness, in 2019 it's exceedingly transparent and clear guide to doing an extremely complicated task. I hasten to acknowledge that's hardly going to be a universal belief.
Maybe Gmail? But again the functionality is fairly shallow...