The goal of whoever chooses the ERP software is to have people make fewer decisions. Whether it takes you 5 or 15 seconds to figure out what to do next/record what you've done is of much lesser importance than what to do next/how what you've done is processed.
That's one facet of such software. But another facet, and by far the largest by ongoing expense (as in amount of people-hours it consumes) is just data input, with little to no decisions to be made. In SAP Concur case, one example I painfully experience is reimbursing business trips. In other cases, this may be timesheets, or inventory, or point-of-sale ordering and invoicing.
The "UI could be improved" is really understating it here - there are low-hanging fruits that could cut down the time spent on data input by factor of 5-10x. This I know for a fact, because I can compare my own experience (e.g. various timesheet & expense forms I used over the years, and the hypothetical case of me preparing the report in Emacs in some structured format, and bulk-importing it to a tool - that's easily a 20x time save), or observation (POS software used in stores today, vs. the DOS-era tools they used just a decade ago - close to 10x the difference).
We're talking extreme waste of money here. Plenty of shops I've seen are bottlenecked on the POS software UI - meaning they either have to let X% of customers go, or support extra registers and personnel. We're talking mental blocks that make people redefine workflows - every place I worked in that required timesheets and expense reports would see people doing them weekly, monthly, or quarterly, instead of daily (as they're supposed to), because the UI is such a time waster that everyone wants to put it off until HR starts complaining, and then back-fill it in bulk. And don't get me started on how shitty UI in healthcare impacts the quality of care...
Sure the UI could be improved, but https://xkcd.com/937/ rule still applies.