The argument that "my app is too complex for PE" is intuitive and popular, but the trouble here is people tend to project far more complexity on to their projects than is actually there. The vast majority of web applications are simple CRUD with some UI polish, but the authors of many such apps think they're building some crazy complex thing that's incompatible with PE. Rarely is that ever the case. I worked on some of the most complex web applications ever written in Silicon Valley and I can say from personal experience the majority of them didn't need a thick client JS framework. The ones that were using them would've been better codebases if they were vanilla JS + a collection of small single purpose modules. Almost all single page apps can and should be built with PE and very few wouldn't benefit from it. There are exceptions, but they're very, very rare.