SAP
It's taken me a while to learn enough to feel confident in holding this opinion, but:
SAP is REAL FUCKEN BAD.
Base SAP is kind of like buying an empty server rack with no doors, and you have to buy every component that you stick in that server rack-- but even after you buy the component, you have to build it by hand with custom built components to make it all work
So it has all the disadvantages of a ground-up custom solution and none of the advantages, and it costs MILLIONS OF DOLLARS.