Almost all picking is done with pneumatic suction because it's highly reliable, powerful, relatively safe and easily adaptable. Furthermore, the standard silicone nozzles on the market permit varying amounts of safety margin due to squishiness. You can solve for almost every real world picking problem without more custom hardware than perhaps a mounting plate and scale instantly to mass-produced parallelism. This is why the industry has standardized on this approach... it's practical, cheap, fast and quickly adaptable.
The other 1% of items is a problem only in the case that the thing to be picked is either particularly complicated and irregular in shape, or has some delicate physical property. The annoying case, which seems to be what you are working on, is large numbers of unknown items.
If you start with recognition that no system will work with arbitrary items (the 'best case' generalized picking system will still be necessarily limited by maximum size of the object it can pick, the reach of the picking/placing motion, the weight it can support, and its accuracy/repeatability), this is a difficult field to justify research in, as while an algorithm aiming at generalizing solutions in this space can probably find a way to use the standard pneumatic approach against, say, the largest exposed flat surface of an unseen item after collecting a point cloud or grasping using opposite surfaces or enclose convex faces with an alternate gripping mechanism, these are never going to increase the generality to an absolute extent. Sadly, with this increased complexity comes diminishing returns, increased cost (sensors, actuators, computation, latency, etc.) and counter-intuitively (unless a major paradigm shift is obtained) also therefore a diminishing market.
Logically, then, the process governing new item ingress for whatever operations you are automating may likely be a better place to spend time than chasing after a non-existent magic algorithm / gripper design to solve for arbitrary cases. For example: "Mandate square boxes" elegantly solves the problem, as per international shipping. You don't actually need enclosed boxes - stackable trays work fine too.
About the only case where random item picking makes sense outside of garbage sorting is very large scale general warehousing for hugely dissimilar items, the sort of problem only Amazon has. For almost anyone else, sacrificing storage space efficiency with boxes or segmenting in to multiple specialised systems are likely better tradeoffs.