I don’t think it replaces all of the tools in RT or anything like it but have noticed that with people just starting out that they tend to have little trouble using it correctly and often it’s all that is needed to get things more or less right. Can’t say the same about curves. Other things like highlight and shadow recovery are still needed for mapping from raw. I used to use UfRaw a lot. It’s approach is pretty basic - curves only really.
GIMP’s auto may be a bit much in terms of what it does to the colour channels so that might best be an option. It appears to stretch or compress all to the same length which does sometimes work out but may need altering afterwards - that can be umm “great fun”
I suspect being able to spec the output span is aimed at web use and viewers with crap monitors. I’ve used it to say shift the black end up by N bits and maybe the bright end down. The centre input slider can then be used to get the mid tone contrast as wanted which is often the important part. I do like the bits aspect been shown on the output and as most things are displayed on a sRGB screen that’s pretty sensible. If the end is Adobe RGB for printing then 0 to 255 might not be a good idea.