Labor is definitely an asset and it is termed as valuable asset. The economic standard of a country mainly depends on the labor force of the country. The more advanced the labor force is in the country, the more developed the country is. Like health is a valuable asset and without good health the body is not good, just as labor power is a valuable asset for a country and because of this labor power a country is prosperous. Moreover, if the developed countries of the world are taken as idols, then you can research there and see that they are so developed and rich mainly because of the labor force.
Labor can indeed be a valuable asset for a country. however, it must be kept in mind that, unmanaged, labor can be a burden. For example, if a proper education, suitable employment opportunities, or decent working conditions are not provided impetuously by the country, then the large workforce can actually become a burden. On the other hand, countries with a smaller population but skilled and educated workforces are often more productive and advanced. Therefore, what is important is not only the quantity of labor but its quality and management.
Apart from workforce quality and management, innovation and technology are an essential factor in a country's progress. A country seeking progress must have a strong technological base. The developed countries have an advantage of making the workforce capable of being more productive because of the technology used. So even though the number of workers is not too much, their efficiency is very high. And vice versa.
This can be called human resources, a country will be able to become a developed country if they have good human resources. For example, in a country that has abundant natural resources, but its human resources do not have the competence to manage it, then it will be taken over by outsiders, or in other words the country cannot maximize what they have from their natural resources.
This is the task of a country's government to be able to create good human resources. As you said, this is an asset, but to create these assets we are required to work hard to be able to have them. How many countries are finally still developing countries while in terms of wealth they have it, it is because they lack inadequate human resources.