Exactly - I suggest we forget the segregation debate, and just treat "Go Dutch" as a call for TfL to do lots of stuff: "we should be able to cycle everywhere like the Dutch do". The Dutch are perfectly happy in practice to do lanes if that's all they've got politics/money/space for, and that's what we'll probably mostly get, because that's the most cost-effective.
I think it depends on your measure of effectiveness.
It's certainly effective if your measure is how many boxes get ticked on forms.
In many circumstances, it may be effective if your measure is how many people start cycling as a result of a perception of increased safety. In my decision to come back to cycle commuting, I certainly was influenced by the increased number of cycle lanes since I stopped doing it 15 years earlier.
If your measure is actual improved safety, then I suspect there are very few places where it is effective. 15 months after starting back, I now wish most of the cycle lanes weren't there on my route. This is because I have learned a lot in that time, much of it from personal experience.
It does seem a bit strange to say "forget the segregation debate" in a post that goes on to say that a very weak form of segregation is "what we'll probably mostly get".
Having said that, I think I would accept the negative results of having more paint on the roads, if it were coupled with presumed (or even strict) liability laws and an education campaign aimed at drivers.
Of course, it's all academic for me because nothing is going to happen about this in my neck of the woods.