This isn't a "bottleneck" but rather a capability (or lack thereof). As you add more and more capabilities, especially ones relevant to enterprise situations like authentication, authorization, governance, etc. then MCP starts to pay off.
If you do not need those capabilities, then you do not need MCP. And then you shouldn't use it. But if you do need those capabilities then it might be worth using MCP rather than inventing your own way to do them.
But for enterprise there may be teams, each developing their own way to do it. Then there will be many different ways that it is done throughout the enterprise, which is hard re: governance. Better/easier to adhere to an industry standard which can be audited, especially for enterprises where that is a legal requirement.
That isn't a reason you should use it, just an explanation about why someone has to use it.
that is basically what MCP is. except it answers all the questions that your version handwaves away - how often do you get a fresh copy, how do you describe the relevant tool calls, how are the tools organized, and how does auth work.