I think one reason Rose was so powerful is that, based on what we know, the versatility of Gem powersets tends to scale upwards based on the Gem's base "power level" to begin with. More specialized castes like the Rubies don't really do much outside of summoning weapons or fire powers, whereas someone like Jasper has a few extra abilities (mainly the spindash, but her ridiculous durability should probably count too). I mean hell, outside of the limb enhancers, from what we know homeworld Peridots aren't even meant to have powers.
But that's the thing: Gems seem to have a pretty wide variety of potential abilities they can unlock, but they're also explicitly related to what they're doing. In a society like Homeworld where a Gem is born and taught that they're explicitly designed for their purpose and nothing else, there's really not a lot of room for them to discover new abilities. Stepping out of line means getting poofed or worse, as with the Gem Destabilizer tech and the energy-fields blocking the holding cells on the hand ship. One of the biggest contributors, though, is also being a society where very little emphasis is placed on the individual, and - based on what we've heard - modern Homeworld has next to nothing resembling social support networks outside of "spires for thinkers to think in".
We even get a potential confirmation of this in Garnet and her Future Vision: while Sapphire's is more linear and its accuracy is inversely proportional to how active she is in a situation, Ruby's passion and impulsiveness allow Garnet to see a lot more possibilities, albeit at the cost (gain?) of being able to sift through them by choice. In this sense, since in an interview Rebecca Sugar specifically noted that it was Ruby who influenced the Future Vision and not that it's something exclusive to a hypothetical "Garnet" homeworld caste, we could see it as Ruby having Gem programming baked-in somewhere that would allow her to modify an ability that she didn't even have.
When Gems are allowed to move past their informed boundaries, we get people like Pearl and Peridot, who - despite what they were told about their capabilities on Homeworld - have gone on to develop tons of additional powers and understanding of once-alien concepts (like Peridot more or less getting her metal powers through empathy for her technology and the power of friendship). So, keeping in mind that Rose:
- Is apparently a very powerful and versatile Gem even prior to rebelling, on par with Jasper and Bismuth if not more powerful
- Gained an understanding (to an extent) and appreciation for organic life
- Gained an understanding of the conditions necessary for organic, Earth-relative life (food, water, shelter, vegetation to provide oxygen, animals for hunting and as beasts-of-burden)
- Led a rebellion that allowed her to fuse with, understand, empathize with, etc. other Gem castes in a major way
- Was specifically noted to have developed deep relationships with humans, mainly men
It makes total sense that Rose's power set is absurdly wide. She's basically the perfect storm of human and Gem innovation in that she started out as a powerful Gem, but also exceeded her imposed limitations and as a result of that she gained (or rather learned how to articulate) powers specifically related to plant life, healing Gems, etc. Then, if you take someone like Jasper who's still mostly operating in the same bounds as before (not including fusion) and was the "ultimate Quartz", she may not have a very extensive powerset, but she's also really good at what she does, which is fighting.
Steven's power set going on to exceed Rose's also makes sense in a way, when you consider that most of Steven's powers are defensive or healing-related, it's because he's also living out plenty of experiences as a human, so his empathy and understanding of organic life is probably going to eventually surpass Rose's.
We even get a taste of this in Bubbled: part of the reason Rose was able to fight off Homeworld for so long was because she gained her healing powers through empathy for her fellow Gems, and empathy is pretty much not taught at all on Homeworld.
