PPB is basically useless because just diving more enables you to learn buoyancy
No no and thrice no!
The core skills (buoyancy, finning and trim) are vital for effective diving. These are frequently appalling in recreational divers AND DiveMASTERS. Nailing core skills makes diving safer, massively easier, facilitates new skills (photography, decompression diving) and protects both others (silty scissor kick!) and the environment (no touch).
No person can (or should if being pedantic) move on to more advanced diving until they have excellent core skills. Especially if doing tecreational** diving, such as wreck penetration, deco, multi-gas, photography.
The dire state of DiveMASTER skills is the root of this. They should all have good to exemplary core skills, especially ALL finning techniques: flutter, frog, helicopter turns, back-finning, etc.
** Tecreational -- more advanced recreational, but encroaching in to technical diving. Deeper, additional gas, moderate deco, overhead (wrecks, caverns). i.e. pushing it to the limits of recreational.