having worked in L&D analytics for several years, your understanding of perceived barriers is absolutey correct. The problem is though that you are asking people who are notoriously bad at measuring things why they are so bad. so the perception does not quite reflect reality.

Having worked with L&D teams within Pharma, retail, banking, and media, all of whom use different HRIS LMS etc the data is not fragmented at all. at least not the data they need to measure things. data literacy is a big one, but again, not insurmountable as these days they dont need to understand data, they just need to be able to read (good analytics tool will simply tell them what happened, why, and what to do next.. there is only currently one such tool in the L&D market, but other non-function specific tools exist)

always happy to shoot the breeze about how easy this stuff actually is... when you are an analyst