That's a really insightful question that gets to the heart of why Industry 4.0 feels so frustrating sometimes! You've hit on a major pain point that many manufacturers are dealing with right now.

The reality is it's a mix of both technical limitations AND corporate inertia, but let me break it down:

First, the technical side: PLCs from 2005 typically use older protocols like Modbus RTU, Profibus, or early Ethernet/IP. These were designed for closed industrial networks, not for modern cloud-connected IoT systems. They lack the security features, data formats, and communication standards that modern IoT gateways expect. It's like trying to connect a rotary phone to a smartphone - they're fundamentally different technologies.

However, the corporate inertia part is real too. Many companies have legacy equipment that still works perfectly fine for basic operations, and the ROI on replacing it isn't always clear. Plus, there's often resistance to change from operations teams who are comfortable with the old systems.

The good news? We're getting closer to solutions. There are now edge computing devices and protocol converters that can bridge these gaps without requiring complete system overhauls. Companies are developing middleware that's becoming more affordable and easier to implement.

So how close are we to true 'lights-out' factories? We're making progress, but it's happening in phases. Most factories are starting with 'dimmed lights' approaches - automating specific processes while gradually upgrading legacy equipment. The full vision of completely human-free factories is still a few years out for most industries, but the technology is definitely moving in that direction!