Well, in a way, I miss Flash. I vastly prefer designing the front end like a designer, not obscure code and the modern way of doing HTML with 10 different frameworks. On the other hand, as my dad always taught me in the 90s, if you let a program do your HTML and CSS, it will be an unmaintainable rat's nest. I have seen what FrontPage, Adobe apps, etc generate. I would love a GUI that creates clean MD Bootstrap and jQuery under the hood, but via drag n drop. Meanwhile... as time progressed, Flash killed itself. I can't blame Apple for killing Flash, but Adobe for the software quality. Particularly on the Mac, Flash was buggy, slow, and across platforms, a security issue. Nevertheless, it was unparalleled for rapid app development and ease of use. I do miss that aspect.
With Dojo, Esri picked the library with the best internationalization at the time, if I recall right from an explanation long ago. However, Dojo is aging, and is a bit slow to load on clients like phones. I can see why they have been looking to become more library abstracted. React is becoming more popular with big vendor support. So we'll see what happens. But it is a big change and hopefully if we pick something (ie React) it will stay constant for at least 5 or 6 years. But to me... Experience Builder is not a replacement for WAB. It is a great compliment. It seems to fulfill the same customer audience that Story Maps do. Great for turnkey sites with rapid development and minimal coding.