And even if you try to avoid Sourceforge, these days, here is just the announcement by Tony Houghton:
https://sourceforge.net/p/roxterm/discussion/

Having just ported some of my apps to gtk3 from gtk2, I don't blame the guy gtk3 is a major peice of crud, if I'd have known the amount hacks and workarounds I would need to put in just to make them run let alone look reasonable, I would never have bothered, as an example I used a notebook with multiple tabs, on 3 different distros runnin gtk3 with minor version diferences ( 3.10 - 3.14 ) using the default adwaita theme, I had 3 different looks/sizes for the tabs.

I have only ported small helper tools from Gtk2 to 3, which did not require a big effort. I do not know a lot about the difficulties nor the consequences on the user-end.

AbiWord has taken a bunch of hits from this update and I am not sure, that most Gtk3-induced bugs have been addressed in the meantime, as they have made me give up on AbiWord.

However, I have also programmed on the same small scale new utilities against the Ruby-Gtk3 bindings. If it is just the porting which causes problems, then the situation will improve, provided they do not-, in the same way, -thrust Gtk4, 5 and 6 on us too soon. As regards the GUI-libraries, Gtk3 does not worry me any more than others.

Using ruby and their bindings would probably hide a lot of bad stuff from you, the simple stuff is OK it's the blatent breaking of API from one minor version to the next that annoys a lot of 3rd party devs, the gt3 toolkit should really been released as libgnome, because it is frankly now too tied to the gnome desktop ( deliberately ) to be considered a general purpose toolkit.