And they _will_ find them. For example, one year I forgot to add a line from one of 1040 forms to my return. I got a notification from the IRS about a year later that I have under-reported taxes.
And with the defunding of the IRS, they'll severely limit the complex audits.
But if you're a rich person with dozens of companies and complicated trusts? Yep, nobody is going to be looking.