No, the argument is that those IRS experts in tax law switch jobs between writing the regulations for the IRS, and then doing "various tasks" for the private companies that work in tax, including lobbying congress for more complex tax laws thus ensuring more people have to use the private tax companies to get their taxes right as opposed to taxes being simple enough to understand without needing help.
While you could lobby congress yourself, odds are you don't really understand tax law in detail well enough to be effective, while they do.
Thanks for clarifying your argument. I disagree though that lack of understanding is what prevents people from lobbying congress themselves. People and even organizations in favor of simplifying the law cannot compete with, eg. intuit's 2.5 million $ lobbying spend in 2018. Why should individual people have to lobby their congress in a democratic system anyway? If you look at polling data on this subject it will show a majority of Americans in favor of tax code simplification. Yet in the past few years we've actually received the opposite.
Everybody is in favor of simplification until it eliminates the complex part that benefits them. Eliminating the mortgage interest deduction harms a lot of people because their taxes go up significantly. (the latest tax reform pushed the standard deduction high enough that most people don't gain anything by deducting their interest - maybe in a few years nobody will care anymore and this can be eliminated)
People want simplified taxes, but they write letters and vote when their taxes go up, so more complex taxes are rewarded despite that want.
While you could lobby congress yourself, odds are you don't really understand tax law in detail well enough to be effective, while they do.