It's the people who have the loudest mouths who will most easily be promoted, just because they are in people's minds more often, not because of skill perse. They will make sure to get enough speaking time, no matter where they are.

Yes, exactly. What this means is that more often than not, the skilled have to learn more skills on top of what they are specialized in. The most successful people I know (not just financially) are highly skilled at a narrow set, but also understand that they need to put themselves out there if they want to be able to apply it at the cutting edge.

I guess it mostly depends on the kind of company you're at, as well as the size of the company and departments. I don't think it makes all that much difference, as long as you have a good, observant boss who focusses on results.

This is true too, but i would say that most companies around the world do not choose supervisors well on average, meaning that there can be a lot of ladder climbers, not observant bosses.

I'd gladly leave that behind and I'd even be willing to work on being more noticable when aiming for a promotion. And hey, there's more to life than work and promotions.

It is not about only promotion or reward, it is also about opportunity. If you like to work on the best projects, you have to be in a position where people are willing to put you in those places. It isn't always easy and there are tradeoffs to be made.