I think technical issues aside, there has been a huge ideological shift from Construct Classic to Construct 3.
I completely agree with this. I do think they are trying to make the best 2D HTML5 game engine possible still. However they seem to be excited about C3 running in a browser, without asking why people would want it running in a browser in the first place. Yes, it's very cool that complex software can run well in-browser, with hardware acceleration and multi threading. Kudos on the execution of this. I'm impressed at what you've accomplished. But why does professional level software need to be browser-based from an end user point-of-view? One big advantage is multi-platform support. But editing a game on a phone is not useful. Any for-PC game will not even work because there's no touch controls set up and/or the game is too demanding for the hardware. Nobody does work without a mouse and keyboard, it's just not practical. Even something like music creation software is a nightmare to use on mobile devices.
It's understandable that they're trying to reach a larger market with the multi-platform editor, but at the end of the day people just wanted another big paradigm changing upgrade. The paradigm change this time has nothing to do with the engine itself, but the editor.
Construct Classic was exciting because it had a great event based language, and the runtime was extremely performant, both in code speed and graphics, it was IMO the best 2D game engine at the time.
Construct 2 was exciting because it broke new ground on the HTML5 front and made the editor bug free and stable, at the cost of code execution speed (since it moved to JS from c++)(I haven't done any benchmarks recently with chrome's JS engine but I believe it's still slower than Classic). C2 was very well supported and they did their best. HTML5 based games are great in theory and they're almost there, but they aren't quite perfect. Reliance is on wrappers and device support. I'm not surprised that the Wii U can't run a "for-desktop" HTML5 game.
Construct 3 brings.. A better editor for all platforms (good for non-windows users I guess), and that's about it. I would even call the browser based editor a downgrade for windows users, simply because almost everything that they've added could have been done to Construct 2's editor. A browser based program will never be better than a native application. Easier to write, maybe. Better for the company for control/update purposes too.
I would never use the chrome based editor for a serious project if I were to use C3 (which is unlikely). It would be static versioned, tested, wrapped windows versions. I can't afford a chrome update breaking the IDE somehow or causing problems. Or what if chrome drops support for feature x or y which construct uses since it's so cutting edge?
The features in C3 are just quality of life improvements to the editor, or things which won't often be used. I've read all of them. Adding them together does make the experience better, but there's no "wow" features to the engine itself to be excited about, coming from C2. Especially considering the hefty subscription fee. Using C2 just makes more sense unless you want to support Scirra.