I haven't looked at the 787 system, but Boeing is typically pretty good at identifying where they need ice protection and where they don't. Note that none of their tails are protected, and they have no history of any tail icing issues. The 767/757 family is only protected on the outer slats. So they can and do identify the minimum surface area needing ice protection, which allows them to reduce the energy requirement.
In doing so, they are taking advantage of scale. We know that the critical factor in ice is the k/C number, which is the ratio of ice shape height to chord length. A Boeing has a large chord; so the same k value, for example from precisely the same icing encounter, will result in a much lower k/C value for the Boeing than for the Cessna single (all other variables being constant, which is frankly impossible to achieve).
In my opinion, too little is still known about thin ice. We have also known for many years that thin, sandpaper ice is very dangerous stuff in the right circumstances.
The real problem with the acceptability of any ice protection system is that the icing threat, unlike the thunderstorm threat, does not produce repeatable results. Other variables in ice shape, such as horn location, angle, and height, runback, roughness, etc. all play a role in the aerodynamic degradation. One airplane may have no significant degradations, and a few minutes later the next guy falls out of the sky. In many cases, the wing performs just fine until the critical angle of attack is achieved. There is no way for a pilot to know what his modified lift curve looks like while in icing, so he takes away the perception that "it carries a lot of ice"...all the while unaware of how close the the cliff, or peak in the lift curve, he was operating. The vast body of successful experience reinforces the notion that we know what we are doing, and allows us to conclude that boots are acceptable. Every once in a while, a booted airplane turns turtle, and it is easy to direct the cause at the operating decisions made by the crew. In some events, that is valid; in others, it is not.
There have been many efforts at developing low energy systems for smaller aircraft, typically using electrical power. Some are very promising. But there is no manufacturing incentive, because there is no metric to use which will point to one or another system as superior. They are all either certificated, or not. And the gamble of building your brand new Super XYZ 100 around an ice protection system that has yet to be certificated or proven in operation is pretty daunting.
That said, to my knowledge, the only hot wing airplanes to suddenly stop flying in ice were being operated without the ice protection system selected on. This usually happens because a lot of crews operating heated wing aircraft are under the impression that a little ice is no problem. That may be true, until you run the angle of attack up the lift curve slope towards the top, whereupon you find that the curve breaks a whole lot sooner than you thought it would.