How come this or things like https://teachyourselfcs.com/ dont exist for other fields like mechanical engineering?
https://mitocw.ups.edu.ec/courses/mechanical-engineering/ It's available, you might need to search for it and look for the flow charts to see which courses are missing from the other departments. The challenge is, in many places, you won't be able to practice as an engineer without going through an accredited program. If you're trying to be a maker or learn more about that, mechanical engineering is probably overkill…
While not literally generally true in the US, in practice, you'll probably be hard put to land a job.
>If you're trying to be a maker or learn more about that, mechanical engineering is probably overkill.
It's not only overkill. A lot of the curriculum that doesn't involve a lab or a machine shop is probably mostly not very useful. Navier-Stokes fluid flow equations have very little to do building things.