Hi there 
Generally world loading issues are due to the amount of data that needs to be downloaded by the browser before Foundry can start up.
This World Size article should point you in the right direction 
World size has the biggest impact on loading times and by keeping your world nice and lean (you want under 30MB if you can), and moving items/actors and scenes to shared compendiums, you can shave a lot of time off of the world loading step.
Another thing that happens during that step is modules initializing, and module errors or long processes that modules execute can lead to another delay or even a failure. I recommend trying with all modules disabled and seeing if the load time issue persists. You can also try to load in with Safe Configuration which disables the modules and scenes for you.