There is a fair bit of open-source content for Mach4, but you have to hunt for it!
We, the users, want Mach to be all things to all machines - but with the variety of machines, that's almost impossible out of the box. Mach4 has a nice, scalable architecture and delivers most of the common things you need for most machines. They've also made it easier to script our own solutions to customise it to our specific requirements.
OK, that does require learning to write the script - but there are some good examples and great videos that explain how all the bits fit together. Why some things are possible / easy, and others not (or at least are difficult).
The ease of modification also means that the screens people have developed are for their own machines, with code specific to them. If you try to run the screen on a different machine, it may not work. To fix it, you need to code - and if you learn to code, it's often easiest just to start with one of the standard screens and hack it about until it looks like, and does what you want.
It all feels a bit daunting at first - but with the help and particularly videos, learning bit by bit is surprisingly easy!