I can't and don't want to comment on other plot packages, but this is how the current maintainer ( all initial developers are gone ) of the Qt Charts module puts it:

I suspect the aim was to provide easy to use module
for simple charting use cases without needing 3rd party libraries, but not
be the be-all-end-all charting solution for all users. That's how I see it
these days, at any rate. There certainly isn't enough development
resources put towards it to aspire to much else at the moment.
( Quote from the qt devel mailing list )

Uwe