It's funny, I was originally going to comment "the worst of Oracle with the worst of IBM" but I prefer the way you put it

Edit: no offence intended to anyone at SAP, IBM or Oracle - I do think each company has a legitimate role to play for rather different markets

To be fair, that is the case for most ERPs. It's not really about the size of the product but rather the important role it plays in a company.

Most ERPs can be quite flexible too, there's a ton of customisation possible. And a whole cottage industry of addons and integrations for every imaginable integration or business model. But the problem is you really screw yourself with added complexity when it's time to update. Then you're really condemning yourself to spending millions on consultants at a time when you might not have the resources. And postponement leads to technical debt.

Hence the idea of adapting the business to the system. Making sense too if you think about it this way: you're not really just buying a system but a methodology.

And another thing is that it makes integration with other companies easier. Makes the company more easy to sell or too acquire other companies and integrate them.

This was true even for Royal Dutch Shell, one of the largest companies in the world. A few years before he retired, my dad led a team responsible for coordinating implementation of SAP and for training thousands or even tens of thousands of employees to work with the new system.

I read recently that not using SAP - or heavily customizing it - in markets where it’s prevalent can break big(ish) companies. Apparently the interface to other companies (from which to buy or sell) is so much easier to setup when all have the same system, that using any other system is prohibitive. If you need to interface with hundreds of enterprises that all implement standard SAP, you become the expensive outsider if you don’t. Integration projects can take years and then fail, with nothing to show for - which can threaten a company’s existence. Better to use standard SAP „off the shelf“ and do as little customization as possible.

One of my customers was taken over during their SAP implementation. The general feeling among management was the work had weakened them so much it made them vulnerable to takeover.