GA has been in decline in aust at the change of government in the mid eighty's. When I started aircraft weren't able to get into the circuit area as it was to busy. Casa don't wont GA its too hard for them to regulate. the prefer the big org because its all kept in house.
Cessna and Piper flooded the market with masses of cheap light aircraft in the 60s & 70s and then were sued into virtual non existance due to liability cases.
From the 80s onward the cost of procuring new aircraft and parts advanced faster than the industry could keep up with. The new aircraft not doing anything particularly better than the old with respect to costs. The prospective users finding other more satisfying things to do with their cash.
New GA types are now hamstrung by costs so not many new types are hitting the market en mass, except expensive tourers. The only trainers being delivered being for large training providers with lots of cash. It is hard to say if these schools will pass them on at reasonable hours to fill the second tier market or just hang on to them until they are 30 years old and worn out.
If it was the Australian government that caused the rot then they must have spread it all over the world.