The OP said:

Pretty much every company I’ve been in or know of values a vertical trajectory instead of a horizontal one for its employees i.e becoming a manager nearly always means a faster salary progression than becoming an expert in one or multiple fields.

Why is expertise valued less?

I simply explained what someone might have meant regarding seizing the means of production being a potential solution to expertise being valued less than being manager.

You still need leadership in any system.

Eve your argument “seize the means of production” only happens with leadership.

I didn’t say we don’t need leaders. An owner or a manager may be in charge but that doesn’t make them a leader.