A decent nvme ssd can read ~35GB of data in 5 seconds for reference.

Or you can download 66MB of data on a 100mbit/s internet connection in 5 seconds.

Say you need to load 1gb from disk and need to download 1MB of data from internet. It should take ~75 milliseconds to do that.

It is incredibly slow, considering Valve is a billion dollar company. This level of optimization is closer to what you would expect from a person who is programming as a hobby.