At best, even if the system does what it does perfectly, it's still a classic "diffusion of innovation" (1) problem where you have multiple stakeholders with wildly varying levels of acceptance. This is always challenging. As those of you who make a living at this stuff recommend, it's better to go 100% with the ERP's way and not customize. Well, that can be extremely difficult or impossible in an environment filled with stubborn beancounter/battle-axe personalities.
Most importantly, however, the people who make the purchasing and sign-off decisions ARE NOT the ones who use the thing. There are going to be problems and those problems will not usually bubble back up to the consultant/vendor. People will just have their noses pushed to the grindstone until the job gets done-- never mind the tedium, never mind the countless little mistakes. New people don't get trained, they just get put in front of the the thing to hunt and peck through it, sometimes with the assistance of a surly veteran of the system, sometimes with no one to help them. There are thousands upon thousands of people sitting in cubicles right now using Oracle EBS with it's horrible grey java applet UI and ridiculous inscrutable query functionality. They've been sitting there suffering it since the 90's. Who listens to their screams? Not Oracle, not exec that bought the thing! Or maybe they're silent and they've resigned themselves to their fate?
ERP implementations are like kitchen remodels. Even when they go mostly right, you hate the people doing the work because they've messed up the thing that's at the center of your home, made you eat take-out for weeks, and dust has gone everywhere.
My clients are all ripping that crap out because nobody uses them correctly anyway. Most of the data in those systems is so error-ridden they're almost dangerous to use. Newer cloud-based systems offer a much more intuitive UI, which ultimately reduces bad data.
Oracle and SAP are basically bad words at this point: you don't say them if you want to get hired.
As for data integrity, I worked in very large SAP implementations without data integrity issues despite thousands of users. I have worked with cloud systems that are full of rubbish.
I recently also wrote my thoughts on what ERP is. Maybe its interesting to someone. https://www.integrated.ee/posts/the-erp-software/
TCO factoring in implementation costs is a fraction of a traditional ERP and is far easier to keep up to date. Most ERP implementations still have a lag of a month or so before data is consistent.
Cloud ERPs stay up to day whether you are ready for the change or not, it is not all rosy when they break important things at critical times of year. Traditional ERPs often don't get upgraded because there is no need. It is simply not worth the testing for the new 'features'. Lots of managers value the stability.
TCO is certainly not necessarily less, it is common for a company to move onto an ERP and stick with it for a decade or so. One off licensing can be much cheaper over this period than some cloud systems. I saw a system where TCO of was cheaper with the trad system after only 4 years.
Cloud based ML models are a bit buzz-wordy for my tastes
At my last job we underwent a transition from one ERP to another. Halfway through it my boss resigned and we got somebody new, mostly on the basis of his experience doing the same at another company. I heard a rumor later that this other company had nearly gone bankrupt because of the roughness of their transition. Things weren't looking good for ours either when I left.
One large ERP project I worked on barely made it past the kick off meeting.... a number of us escalated that we were not happy with the implementation partner so our boss (bravely) recommended that the entire project get canned - which it did.
It's a common joke for senior technology leaders at industrial companies to ask eachother "so what was the first ERP implementation you got fired for?"