I think it's important to distinguish user groups. No solution is best for all of them.

For scientists or data analysts, jupyter notebooks are a great choice since they mirror the professional and research tools they'll use.

For web development, an in-browser IDE like Cloud9 would be my choice to get an arbitrary room of adults up to speed.

But for middle or high school audiences, or even adult beginners, solutions like the above are far too complex. It's easy to get a certain expert blindness, but a Jupyter notebook for instance can actually be a huge problem form someone trying to understand flow of control, since you can execute code blocks in an arbitrary order into the same runtime.

Tradeoffs between power and usability abound. Jupyter is a good blend. A full IDE is power. Skulpt prioritizes usability. Some group of users fits into each of these buckets.

So (surprise, surprise!) The meanings of 'best' and 'terrible' are highly dependent upon specific user needs.