Can WWII tanks still be effective to some degree in modern time?

It's not necessarily about whether they would be effective or not. They would require a ton of money and fuel to transport and operate, which would reduce their effectiveness because there's an opportunity cost at stake. Overall it just isn't worth it to employ them in combat because you could have spent that time/money/space on something more valuable.

 

In a fight, the WWII tanks might be able to disable a modern tank if they attack from the rear with the element of surprise, i'm not 100% sure, but i think a 88mm could penetrate the rear of an abrams tank. In a head on fight, where the abrams knows the general direction from where you are coming, it would be like shooting fish in a barrel for the modern tank crews.