In the current state, LXQT is a beta desktop that feels like a heavy alpha. A lot of the tools and underlying features are in a testing state, while the LXQT project itself has not had a gold (1.0.0) release as of yet.

As all Qt desktop environments themeing is hard since you need to know C++ , there is a sideway using qss however its not as powerful as GTK, Enlightenment or Windows theming.

This is a very disappointing desktop environment, it's very buggy. Although there still is hope that these issues will be resolved.

DPI settings are not adopted. The readability, usability of this DE on UHD screens is not advisable. Fonts are not scaled at all.

Very few themes available, especially modern themes.

Even the programs/apps shipped with LXQt are from the KDE project. They don't have their own projects yet.
It's pretty similar to Budgie that depends on Gnome for almost everything.