They may want better terms, but that does not negate the money they do get for zero investment.
Trying to renegotiate free money would be like ABC turning down advertising for Universal or Comcast. WDW and Universal studios theme parks are competitors, but on the grand scheme their parent companies are both competitors and suppliers to each other, they may even be partners at some level.
Disney bought marvel to make movies, the Themeparks were an afterthought to that purchase. As long as they keep getting a check from Universal for doing nothing I think they will be happy.
The ONLY reason this contract exists is because it pre-dated Disney's purchase of Marvel.
If the licensing agreement were not already in place, Disney would not have given those characters to Universal. Similarly, Disney still owns Marvel rights on the west coast, yet they obviously have not licensed them to Universal, Knotts Berry Farm, Magic Mountain or any other entity. Same conditions would exist: free money, no capex, control over character use, people would keep coming to Disneyland.
Disney will never create a theme park attraction around every character in its vault, but SOP is to leave those properties dormant--available for future use--rather than license to the highest bidder.