The dark mode has nothing to do with if a GUI is modern or not.
It is the functionality of the GUI, i.e. how the user can work in the GUI that makes the difference.and makes it modern. And if it is configurable.

It is only a user preference. Some people like it (find it easier to work) in dark and some in light mode.

Some people have very hard to read and use a GUI in the dark mode.
The problem with the industri and some developers is that they think that they know what is optimal for the user experience, but they don't!
They think a modern GUI must be a dark GUI and some don't even provide an option to switch between modes.
(It seems to be a trend thing rather than based on user experience)

I never buy a software with a GUI that only has dark mode and can't be switched to a light mode (i.e. too dark mode with no options to configure the intensity, colors of the text).
Why? it is useless to me, many times I can't read the text (dark grey or dark colored text on dark background) and I know that many users have the same issues with dark mode.
It is very different between users what is optimal för visability and it might be hard for many with no issues with the dark mode to understand that many people have big problems with this.

Otherwise I agree in full with JJJ comments above.

The good think about the new BIAB GUI is that the user can switch between light and dark mode as they prefere. So it is not an issue.Very good.

It is very important for software with a dark mode to have the option for the user to configure and select, fonts, intensity and color of the text so it will be readable against the dark background.

BIAB dark mode is not so dark so it will work fine. But the user need to be able to configure the color of the text eg green on dark can be very hard to read for some users.

Colors can be very pretty but the main issue in a GUI for the user is usability i.e. to be able see and read the text and information with ease. So for that purpose it is always better to use white text on grey background as default when in a dark mode and let the user configure other colors for the font depending on preferences. As an example in BIAB the tiny mixer box in the multipicker view is completely useless for me dark green text on black background. I can't read it at all in there (what a shame).

For the same reason as above I would like to be able to configure the colors for some of the text in the BIAB mixer and the track view (eg green on black background not very easy to read, especially not in the multipicker mixer view). I have not found any options for that, but maybe I have missed it.

BIAB 2025, Studio One 7 Pro, Song Master Pro, Win11 Home. i7-9700K CPU, 32GB, ESI MAYA44eX, ZOOM UAC-2, Guitar Pro 8, Transcribe, (EZKeys2, EZD3, SD3, EZBass, EZMix3)
Amateur: fiddle, guitar, vocal, beginner on bass.