To be fair: If you fully rely on the ST tooling, setting up even something moderately complex, peripheral wise (like a bidirectional UART <=> USB bridge) is very straightforward because you get all the configuration/software stack just from clicking a few things in their GUI tool, then write a few lines of API calls and you're done. It's gonna be neither pretty nor especially efficient (specifically STs default HAL interrupt routines tend to be atrociously wasteful), but chances are good that it actually works immediately.

But if you want to do that from scratch with little experience, you are almost invariably gonna miss like 5 different clock/IRQ/peripheral enable flags, get some clock prescaler wrong, missconfigure a GPIO pin or two and then spend a bunch of time tracking things down with debugger, reference manual and scope...