The reason they're so strong imo is because of their W+Q providing a lot of mobility early game and ult allowing easy dives,also combined with bloodrazor that's getting buffs and synergises extremely well with Kindred and new dragons since they can take drake fast with a stack or 2 or just gank bot and get dragon afterwards
E is also really strong but that's the only thing that makes Kindred able to gank in the first place,they don't really have high burst like a Graves jungle or something so losing that big chunk of damage + their only CC will make ganks horrendeous if they miss,Lee can still do something like walk to cut off the enemy,ward hop behind the enemy to ult even if he misses Q
anyway my point is that E is really strong,but making it a skillshot wouldn't make much sense thematically and it'd make Kindred's ganks extremely bad if they miss E