So if a switch from Canvas2d to WebGL would be made, this fellow user would be "argh everythings fine".
As i said, just let it optional. So the users can switch betwen those two.
Well while I do like the option to allow people to do more if they want to explore developing with WebGL, Scirra's mission statement is to have C2 to be supported on older computers.
On these computers the end user doesn't even know what WebGL is, and would not know how to enable it IF they can. While most computers nowadays support it out of the box and the older ones drivers can be updated to support it, it's only really transparent on Node-Webkit. Browser based games they would have to enable flags, or update their browser version.
Lots of those requirements are very easy to do on PC, but mobile devices with HTML5 support do not have it that easy. Many of them run worse WITH WebGL enabled. Scirra does not like introducing a feature that requires too much WebGL without really having a go at Canvas2D implimentation first.
They could've made the tilemap plugin webgl only, but they worked at it and their implementation of it is wonderful. Perhaps in the coming years they could not put as much importance on canvas2D, but legacy support is very important at this moment in time. Plus if they can make it work for Canvas2D, it will work smoothly for WebGL and that's important too.
Out of curiosity: how it was made in CC? It worked perfectly there.
.CC used DX9 as it's foundation so it had more access to the video card. WebGL is essentially that, however Canvas2D is a bit weaker as it was designed to be simpler.
For animation I heard you can simulate that via "load from URL" in your events, although since it's part of the existing TiledBG I don't see why they could introduce filling from part of an image based on how the Sprite object splits and loads different sections of an image. At the very most it could create multiple images instead of one stitched image, if the area-fill command messes up with a image section.
Offsets and rotation, other than moving the object itself, would probably either be very tricky for Canvas2D, or WebGL only as it's more intensive on graphical manipulation. If they were WebGL only though, they would still have to not crash/make Canvas2D run any slower as well.