Re: They shouldn't have broken their copy of ECC in the first place
I think these comments are missing the forest for the trees. Yes, we over customized the original implementation, but that was required to make it work for the business in 2000. ECC had deficiencies and yes, the tech underneath it has changed. But that is not what's justifying the S4/HANA migration, at least where I work.
The way the business runs has changed since 2000 and there is too much legacy business process debt built into ECC for it to keep up and keeps the lights on, as there would be in any 20 year old ERP. Digital supply chain, Enterprise PLM driving shop floor operations, and Day One acquisition financials integration are what the business wants now: Each of which would be hard to incorporate into a 20 year old monolithic system, and together justify the sea-change.
And it doesn't have to be that disruptive, at least for the Tech folks if you crawl, walk, run. We started with BW to get our feet wet with S4/Hana. Then went to CFIN with a Enterprise side-car. Now planning the build out on that, while ECC keeps chugging. Doing it in the cloud just accelerated the machine builds because there we no PARs to sign, but the details didn't change too much. The cultural change in digital transformation is MUCH harder to achieve and the real challenge here rather than the underlying tech.
Just an opinion, and YMMV, but the business is changing radically around us and we are going to have to change with it.