Your attorney will mediate between you and the IRS and help you to reach a negotiated settlement. Where disputed amounts are large, it is usual for the taxpayer to reach a negotiated settlement for a much smaller amount than the original claim. This is why people employ tax attorneys. If the case goes to court then you will be represented and have the best advice available, a much better position to be in than facing the might of government alone.
There are so many complexities to every tax system because of the cumulative effect of thousands of pressure groups over the past 200 years. Each group manages to persuade the government of the day that they will get more votes if they accede to the group’s demands. The government acquiesces and another complexity is added to the tax regime.
Many of these pressure groups’ demands could be reversed, but that would require immense political courage, which is not present in most democratically elected politicians.