The StarFive Debian 202306 image is an engineering release, the kernel enough to bring the board up to allow work for upstreaming to the Linux kernel. And because of that it does not have all the bells and whistles, it is a longterm 5.15 kernel with enough modules enabled to support the unique hardware of the board.
An engineering release is intended to bring up the hardware for software developers to be able to work. Adding ALL modules would just slow the speed of test builds. Even though it may only add a few minutes there or seconds here to each test build, that cumulatively will all add up to a substantial amount of wasted time which ultimately will slow down how fast the unique features are upstreamed. <<== StarFive have been doing totally amazing work, in upstreaming.
If you want more bells and whistles but do not mind loosing hardware accelerated GUI then look at the current alternatives (At least until Debian Trixie, which will be the very first official Debian release to support for ANY RISC-V hardware). Or else just add the modules you want yourself to the existing kernel (VisionFive2->Software Document->SDK Quick Start Guide).