What would you recommend instead for the ones that would be interested to start learning robotics stuff? (Not trying to be snarky but actually curious)

If you are a hobbyist, academic or garage startup, absolutely use ROS. It will take you from nothing to something faster than anything.

But, the moment you ship your first product, open your task tracker and add “Epic: Migrate off of ROS to a custom framework”.

Source: I’ve been working full time building a custom ROS replacement for a large company for several years. Results are good.

When robotics moves from the lab to the field, expensive certainty becomes more attractive than cheap flexibility.

For what, specifically? ROS is a collection of different mostly-independent components. Just write the code to do what you need, or use normal libraries to do specific things they're good at.