Actually, I really like these two GUIs which build on the strengths of R by combining the data-exploratory tools that Hadley Wickham created with the visual appeal of ggplot2 (also Hadley!), plot.ly, etc;

1. https://exploratory.io/

2. Radiant: https://radiant-rstats.github.io/docs/index.html

Microsoft IDEAR looks good, too:

https://github.com/Azure/Azure-TDSP-Utilities/blob/master/Da...

In addition, the automatic insights generated by Power BI are another example of how GUIs can help even the hardcore command-line ninja:

https://docs.microsoft.com/en-us/power-bi/service-insights