Combinations.

Unique utility prevails.

Adaptability is not imitation. It means power of resistance and assimilation. ~Mahatma Gandhi.

There used to be a time when a single doctor used to treat all kinds of diseases throughout the body. In roughly the same time frame, all the engineers and artists used to build stuff.

It used to be:
Doctors - One for all.
Engineers - All for one.

These days, it's slightly different.
These days we have many super-speciality doctors who focus on one organ or body part. We also have engineers who take care of different things.

The world today looks more like:
Doctors - One for one.
Engineers - All for all.

In rare cases, we do find general physicians who take care of diseases at the early stage. We also find engineers who are good at only one particular thing. They have their roles to play, but as we move forward in healthcare, we will need doctors who know all about that one thing and engineers who know more than just one thing.

Today engineers find themselves in a situation where having one skill is, more often than not, insufficient. We need to have as many skills as possible.
How much you can do is directly proportional to your preference, as people here seem like a jack of all trades more than a master of one.

We are a population of almost 8 Billion, and according to LinkedIn data, there are around 50,000 professional skills.

It is said that an average person has up to 700 skills ready to be used anytime!
Most of them are basic, and the others are advanced.

I realised this a couple of years ago and also said it before. A unique combination of skills is more likely to help you stand out from the general public than your mastery of one specific skill.

Explore your interests, find the need in that field, and develop relevant skills.
If you do these, you will be unstoppable.

If I were to describe the term "Skill", I'd say all the things a newborn baby can't do and advanced versions of what they can do, are skills. 

New-borns can't speak. Hence, speaking is a skill.
New-borns can't think. Hence, thinking is a skill.
New-borns can see. Hence, observation is a skill.
New-borns can hear. Hence, listening is a skill. And so on.