Monolithic architecture, over a period of time, will remove the agility of a team, which will delay the application rollout. This means people will tend to invest more time in finding a workaround to fix a problem when a new feature is added or something in the existing feature breaks. The monolithic architecture will bring a greater amount of inefficiency for larger projects, which in turn, increases the technical debt.
Microservices, on the other hand, reduce the technical debt in terms of architecture since everything is reduced to individual components. Teams tend to be more agile and they will find handling changes easier.
The less code there is, the fewer bugs there are, meaning less pain and a shorter time to fix.