How can it take MULTIPLE YEARS to go 64 bit?
Sounds to me like they had pretty much stopped making any changes to the software other than maybe regulatory rules (i.e. new laws that change how accounting works) and have been found out.
For well written software it is just a recompile and some extensive testing. For a "30 year old codebase" that I guess is a spaghetti monster of hacks dating from the MacOS System 7 days I suppose it would be more involved. But I wouldn't want to trust my business to such crap code when there were better alternatives available. It would be like someone running Netware in 2020.