Yeah Sony has had a long standing practice of unloading these kinds of features on developers instead of providing a broader solution. It doesn't mean they won't eventually get their act together, but until then it's up to the development studios to decide if they are going to implement it and how painful it will or won't be.
Sony does need to get their act together and work on this.
Interestingly enough, there are some older games on Sony systems that
do have easy and seamless cloud transfers with little or no intervention from the user. Most of the games that did this were smaller downloadable games.
CounterSpy was one such game for PS3/PS4/PS Vita, where you could play on one console, finish your session, then play later on a different console and instantly resume where you left off. You didn't even need to choose to upload your save, as the game handled it automatically. (I believe the user could disable this through a menu option, if he wanted to progress with separate saves on each system.) CounterSpy had its online services terminated a year or two ago, so this might not work any longer.
There were several other games that did this. Some games required you to select an in-game option to upload your save to the cloud, while others did it automatically (such as CounterSpy described above).
It's also worth mentioning that the functions in these games apparently used their own servers to handle this feature. This means that you don't need a PS Plus membership for the games to sync your save data. The disadvantage of such a method is that it is dependent on the developers to implement this themselves, and also maintain the servers and keep them running.
Ideally, what Sony should do is implement this function themselves, through Sony's own servers. They should also
enforce it, so that games submitted after a certain date
must contain this ability (similar to what they did in the past with trophies). Bonus if they can do this without requiring the user to pay for PS Plus. Future games should have cloud syncing enabled by default, but also allow the user to opt out if he desires to keep progress separate on different systems.
It is the first Sony console to have full BC since PS1->PS2. On the first BC PS3s, you couldn't import any saves if I remember correctly (maybe via hardware adapter).
Early on, Sony produced a memory card adapter for the PS3, which could read data from actual memory cards for PS1 and PS2. This adapter was apparently discontinued after less than a year, so they might be hard to find now.
Once the data was on a "virtual memory card" on PS3, you could also transfer to other Sony systems such as PSP, PS Vita, and PSTV. For example, I transferred my original data from Wipeout for PS1 to the PS3 using this adapter. As a result, I was able to use my Wipeout data on
six separate systems (PS1, PS2, PS3, PSP, PS Vita, and PSTV)!