Yes, its a hard dependency. But we go out of our way to add CSS classes to our UI widgets and even have a configuration in Ghostty to supply custom CSS directly (without you having to mess with gsettings or anything). We've seen some pretty incredible customizations in our showcase channel in Discord.
We haven't committed to our CSS classes yet as a stable API but we plan to do that in the next release cycle. Still, they haven't changed much in a year. :)
You are projecting. Personally speaking, I would choose Electron waaaay before I'd choose GTK. That probably wasn't an option for his optimized terminal, but would be Good Enough™ for just about anything else.
Electron is bringing an entire web browser in to provide a cross-platform user interface. GTK has become almost a web browser to provide a cross-platform user interface. That is why I started off with
Their CSS implementation is broader than what most actual browsers had 10 years ago. I would not have commented if I weren't already painfully familiar.
We haven't committed to our CSS classes yet as a stable API but we plan to do that in the next release cycle. Still, they haven't changed much in a year. :)