This seems to be splitting hairs on what an “idea” is. Is a patent on the use of water heated into steam to drive an engine different from the idea to use steam to drive an engine? I don’t really see where you draw the line here, and the idea to use steam to drive an engine was definitely new at the time so why shouldn’t it be patentable? And also note that your linked story does not implicate the US patent system (which addresses the problem you’ve identified: your patent only lasts for 17 years, not for your or your competitor’s life) but seems to be reliant on the British patent system as it was in the late 1600s.

You can argue that the patent system in the US is partially broken because of how broadly patents are granted nowadays, but that does not support the GP’s contention that there is some kind of distinct line that can be drawn between an idea and an invention, which is why the patent system is what it is now. And, again, your own link underscores how far we’ve come in understanding that unlimited monopolies on technologies/ideas are bad and how limiting patents durationally can help with that. Note that one of the requirements for a patent to issue is called “enablement” which basically means that your patent MUST describe the invention with sufficient particularity that a person with ordinary skill in the art could make and use your invention.