ERPs are tedious, uninspiring, production-level software that have to deal with all manners of ill-defined business rules and variations. It's almost impossible to come up with an elegant product because the problem space itself is inelegant and in many cases irreducibly so. I imagine it's hard to attract talented developers (except those solely attracted to money) to this space because the feedback loop and intellectual payoff is so unrewarding. Most of the time the implementation problems have to do with human problems, not technical ones. Most ERP customization is outsourced to pools of fungible labor.

But when you run a large enterprise, ERPs are absolutely necessary, so someone's gotta do it.