A large population for some countries is a positive thing because a large population can be used as a subject for development, the economy will develop if the number of workers is large. A large population, if accompanied by adequate population quality, will be a driver for economic growth. On the other hand, a large population combined with low quality makes that population a burden on national development.
A large population can also prevent a country's economy and development from developing quickly because it will be difficult to develop competence human resources, especially if the country is a poor country. The quality of a country's population will be seen from the education they receive and the jobs available. For poor countries, this is far from expected because the government's focus must be on building human resources first.
So in my opinion it doesn't have a significant negative impact on the economy in a country with a large population, it's just that the government needs to increase its quality human resources with quality education evenly and be able to master technology so that it can help the country to achieve development targets.
Whether the is negative or not depends on the leaders of a country, whether they are able to develop human resources or not, the availability of job opportunities can also be seen to what extent the government can develop. Poor countries definitely have far fewer human resources and it is difficult for them to develop skills because the education rate there is very small.
However, if it is mismanaged it will really make the situation worse. The large population and its high growth rate have consequences for the difficulty of finding work, high food prices, education and health costs and many social problems due to the large number of unemployed and so on.
Governance depends on the vision and mission of the leaders we have. If a leader comes from ideas and concepts, perhaps this will be easy for them to develop, but if leaders are born from the opposite, it will be very difficult for them to develop human resources. Many other problems will arise if the population is too large and the country is classified as poor, even worse if the country does not have natural resources that can help the government in building human character, development and a sustainable economy.