HOW ABOUT YOU ?
To me the difference between #senior and #junior is :
senior able to teach and junior able to learn this much depends on technical skill.

The senior has to be able to learn as well, or they won't be working as a dev for much longer...

I like the view where:

Junior: Does not have autonomy over their own work (ie, needs guidance and orientation)

Mid-level: Has autonomy over their own work

Senior: Has autonomy over their work and that of the less-senior members of their team. (Provides the guidance and orientation to the juniors)

If you are good enough you can become a senior instantly. You just have to have a lot of motivation to push the project through and not give up at all.