I had to stare at that to be sure which was firefox and which was tk. I agree the defaults sort of suck but you
can tweak them and make it look pretty decent.
If Tk was all I had, I'd probably sink the time (and it would be a lot of time) into learning how to fiddle with xrdb (for tk) and ttk's styling engine.
The lack of documentation, opaqueness, and complexity, all that stuff adds so much challenge, just to get to "pretty decent".
There are better options in 2016, both from a visual perspective (looks good out of the box) and a programmer-tweakable perspective (can I make changes?).
I said this elsewhere, but Tk brought something to the table a long time ago, when GUI programming was complicated. GUI programming just isn't hard, the way it used to be.
Hey, if you're used to it, great, I certainly don't want to take the option away from anyone, but it's misleading to offer it as competitive in any way with the other contemporary toolkits.
http://www.mcvoy.com/lm/bitmover/lm/gui-config/gui.html
I had to stare at that to be sure which was firefox and which was tk. I agree the defaults sort of suck but you can tweak them and make it look pretty decent.