Dark theme is a basic accessibility, a lot of people have sensitive eyes.
The Widget Style under 'LXQt Appearance Configuration' can be set to use what ever colours you like, and there are 'LXQt Themes' as well, where you should be able to select between a bunch of dark themes already.
Sorry, you are right, now LXQt is dark for me :)
Glad it's working out for you, and thanks for reporting!