Hi Aditya,
Good day to you!
You're getting this warning because your design is large and it contains larger number of nodes that you're trying to simulate with free version. It also cause the execution time to increase.
ModelSim*-Intel® FPGA Starter Edition (No License required, Limitation in design size), where as ModelSim*-Intel® FPGA Edition (License required, No Limit in design size).
Kindly check the difference for both edition in link below.
https://www.intel.com/content/www/us/en/software/programmable/quartus-prime/model-sim.html
Thank you.