It really depends on the tool… CRMs and EHRs are often designed to be customizable. But end-users typically don't want to spend a lot of time configuring and customizing the interface itself. All the choices quickly become overwhelming.

A "customizable" tool for any task sufficiently complicated to be someone else's profession inevitably results in a tiny micro-economy of configuration engineers who specialize in customizing the tool to be just so.

But the crazy thing is this is still a better solution in the majority of cases than not offering extensibility at all. It turns out buying one piece of enterprise software for $250,000 and hiring one specialist in it for $150,000 per year has historically been a better deal than dumping millions into building it yourself. The gains in efficiency for the fifty $400,000 per year doctors, and 500 $100,000/ye nurses, etc who use it are still worth it.