I think there is a middle ground of many indie games I see on steam that are much larger then they should really be.

As a dev, one problem I saw often is UE4 is massive, well over a hundred meg for just the base engine.

Binary size is a drop in the ocean most of the size of game installs is in assets.

While true, you do have to ask how the hell there could possibly be 100 MB of just code.

Consider Windows calculator. In Windows 10, it consumes 15+ MB of RAM. When desktops have 8+ GB of RAM, 15 MB is essentially nothing. And yet, 15 MB is an astronomical amount of RAM considering the functionality Calculator offers. There's really no reason it should be more than a couple hundred kilobytes.

I didn't have a look at the code but the binaries aren't just code. Apart from things like embedded icons and stuff, there can be lots of engine embedded resources inside;

You can actually look at the UE4 source and see.

There is a reason for that, which is that UE4 has an absolutely massive amount of features out-of-the-box compared to most other engines.

If you were to add all the stuff from the Unity marketplace you need to be equivalent to a base UE4 install, it would probably approach that size as well, presuming all those features were even available.