Given this only became a more prevalent issue in the last 2 years (jg has always been vital, but now more than ever), the solution is jungle monster tweaks.
Due to the inability for many to solo drake early, long camp respawns, fatter camps (punish slow clear junglers for failing ganks) and far less vision than previous seasons. A gank fest is all that remains for anyone.
So the player who can go "that lane will push back towards me on its own, I'll wait", "they won't have it warded in 60 seconds", "their jungler will be here, let's counter gank/jungle" or "this gank is a waste of time, I going to gank X instead" faster, more proactively and more efficiently than the other will be the better jungler.
These are hard things to improve on, as trial and error are the only ways to do it. Game sense takes a really long time to get a good grasp on in relation to your skill rank. The answer to a bad gank opportunity is no longer "go back and farm farm farm" because riot changed the jungle to stop that.
Too often I find that lanes aren't good enough to be worth ganking (not bad players. Bad circumstances): lane is shoved in (Don't wanna risk a dive), we won't come out on top, one of us will die, they're really hard to catch with a gank/kill, they warding too well ect.
But my jungle has been fully cleared, I've used my wards, killed scuttle and now I quite literally have nothing to do. I could invade, but depending on the champ it may not be an option. And if I do, can I make it worth the risk?
There's no longer a choice between power farming and ganking. You gank or you lose.
So. Revert jungle changes. Give the buffs their minions back to slow down the stronger champs and speed up the weaker AOE ones. Reduce respawn times so farming isn't an impossibility and for the love of god give us more vision.