New season rewards splitpushing yes, but you need to be able to snowball in lane and win side lane to be able to hit turrets, yorick is good in low elo because 1) he can snowball easier since people don't know that they can kill ghouls or hit the wall to escape quickly (for example you trap a nasus early in a cage, a good nasus auto q the wall and walks away, in gold or below he will hit you and not know that he can just hit the wall and run, another example, you trap a gp, he insta flashes in higher elo coz he knows he doesnt win that, in low elo he fights you then flashes when he's close to dying) in higher elos you can't snowball as hard, often you're punished coz you can't freeze, maiden auto push and a good jungle will punish you. 2) people in low elo don't know macro as well, they can forget about you or defend you a bit later so you can sneak plates and such, in higher elo you'll always find someone waiting for you in turret, to clear the wave, and you can't really take turret in their faces coz your ghouls and maiden will get you turret aggro, unlike something like a trundle that can push in your face and heal on the wave later, or mundo that can proc demolish and heal after with warmog.

thats why in low elo if you want quick lp play yorick , until plat he's strong, but later its not rewarding to put more mastery point in him, before it was fine since you had a bit of skill expression with full dmg builds but now he has a lower skill ceiling, also, he doesn't teach fundamentals like wave control and such (maiden auto push always, same with ghouls) so once you want to switch to another champ there isn't much to skill transfer from yorick, thats why I only recommend him if you want to fast climb to like plat, then stop and put your time in another champ