Let's look at the facts here, this will no doubt be a biased OP because this is my personal opinion. Feel free to argue or rebuke the point.
Based on what we have seen from Jasper, Aquamarine, and even Lapis, Homeworld is x100 stronger than the Crystal Gems as of now. If they wanted to take over Earth, they would have done so.
So, we can conclude that the Diamonds are not worried about Earth because they think they still have The Cluster to gain from it, and that The Cluster is still trying to emerge. Someone will notice eventually that The Cluster hasn't risen, and at that point they will go in and make sure the job is done.
Going back to Rose Quartz, we can conclude that Rose failed to keep the Diamonds from Earth, because they simply used Earth for a different purpose.
Furthermore, Rose tried to wage a war of attrition while at the same time not waging a war at all; as we saw in "Bismuth" we know that Rose refused to shatter anyone. Even the enemy. We can assume that they only poofed or incapacitated the enemy. That means Rose tried to flex her rebellion's muscles at the Diamonds, but never did anything significant to halt their progress, like a bunch of teens vandalizing a construction site. Her Rebellion was the North Korea to the USA. All bark, no bite.
That was, until The Diamonds were gonna go through with the colony anyway. Her attempts to annoy the Diamonds to submission didn't work, so she took measures, which included shattering Pink Diamond, breaking her own morals to try and save Earth in a last-ditch effort.
Well, it ended up screwing Earth over, causing The Diamonds to Hiroshima and Nagasaki the rebellion with mass corruption, finish their unethical gem-experiments, and plant a giant Geoweapon that would assure Diamond dominance over the known universe forever.
I think it's safe to say that her rebellion didn't exactly pan out. At best, her rebellion was a Pyrrhic Victory.