That’s a lot of things to deal with. Especially if you realise that all of these parts are connected to a single database and they rely heavily on each other to work. Imagine now that one part is broken and affects whole internal infrastructure.
The monolithic app is easy to build, but it is also really painful and cost-generating when changing or expanding. There are some pros: it is a great solution for a start, known as an MVP, and quite good for maintenance if you do not grow, keeping the same number of features, products, customers, and traffic.
The problem appears when it comes to flexibility and scalability. Once the enterprise grows, the expectations and needs increase, and keeping everything under one roof turns out to be limiting and blocking. The solution is microservice architecture.