How does Thought Sponge interact with Yarok, the Desecrated?
Unfortunately for you, Thought Sponge won't trigger again. In fact, it doesn't even trigger at all, since it is indeed a replacement effect:


  614.1c Effects that read “[This permanent] enters the battlefield with . . . ,” “As [this permanent] enters the battlefield . . . ,” or “[This permanent] enters the battlefield as . . . “ are replacement effects.


and as you noted, replacement effects are unaffected by Yarok's ability.

A similar card which is affected by Yarok is Propeller Pioneer which has the Fabricate 1 ability:


  When this creature enters the battlefield, put a +1/+1 counter on it or create a 1/1 colorless Servo artifact creature token.


This is a triggered ability:


  603.1. Triggered abilities have a trigger condition and an effect. They are written as “[When/Whenever/At] [trigger condition or event], [effect]. [Instructions (if any).]”