If you want to work *for yourself* on weekends and evenings to level up then sure, do it.
I wouldn't have the freedom I have now without doing that in my 20s.
I just wouldn't have the career success and freedom that I have today if I had done that.
Companies should absolutely not require you to burn the candle at both ends as a regular way of doing business. If you do that for your own reasons, it's fine (it's what I did). Just be mindful and take care of yourself and your relationships.