This might be a tricky question, but having dug in deep with ROS I am noticing the complexity that one has to deal with.
Simple Arduino programming is much simpler but of course can’t do many useful things. No threading, IPC, and many many more. To be clear, I am not planning on using an Arduino, I am just using it as the extreme end point of a spectrum.
So my question is, is there another package or library or framework that does some of the things that ROS does but perhaps not at the level of sophistication?
Thanks to the responses so far, and the feedback. I've added below and updated above.
As an example application, let's say an experimental (i.e I am not trying to build a commercial product - yet) mobile robot, with a depth camera, Lidar, and wheels, that can navigate indoors and be controlled over WiFi. It would likely include slam navigation and/or fiducials. Obviously I am OK with buying the hardware or the hardware components and doing a lot of programming. I would prefer something other than C++ but that's not a strict requirement.