It has been claimed that the US tax code is more than 60,000 pages long.

The current IRS system was developed in the 1950s - 1960s and is built upon aging legacy code and hardware which may not be maintainable.
The last time the US federal government attempted to modernize its systems was after the affordable care act was passed in Obama's 1st term. A new website was built to allow new healthcare signups to apply for aid over the internet. End result, the website ending up costing in excess of more than $1 billion dollars and contained may bugs which persisted for months after the website was rolled out.
Now it seems the current administration is devoting funds and manpower towards the task of modernizing the aging IRS system. If a healthcare application website for obamacare costed taxpayers in excess of $1 billion. i can't imagine how much modernizing the IRS system will cost. It is possible that the project will never be completed or built to satisfaction. Given the known length and complexities of the US tax code. And the existing legacy code not being the most portable.
Before now my country had no digital database of all its citizens. Everything about its population was analog,using the data collected from census. Few years ago the government decided to digitalize the entire population system and ensuring that everybody has a personal identification number. This process is costing my country a whole lot of money. But the truth is that it is worth the cost because financial and other transaction have become easy and smooth because of the personal identification number. Criminal activities now have reduced because of the existence of an identity data base. If the US government is sure that the country really needs to modernize its systems and the cost is worth it, then it is a good decision. But they most ensure that a sound analysis of the merits and demerits of this modernization process have be carried out before approval. And the project should not be abandoned. At the onset my countries digitalization process there were some technical problems, but gradually it was resolved. And the services of the agency incharge keeps improving. The US might face some challenges on the process of the modernization of the IRS system but it would definitely be resolved. I am sure that the modernizing the IRS would make the system more effective and efficient because it would be redesigned based on current realities.