Yes, unless there is a "deep throat" in the FBI who leaks the information to the press, Mueller cannot charge Trump with a crime. Attorney General Barr must make a maximum disclosure so that Congress can decide.
Unfortunately, Trump's hand-picked Attorney General, William Barr, can hush it up. Or Barr can seal the records for fifty years like they did in the JFK assassination and Nixion's Watergate scandal.
Trump's inner circle, a group of Republicans and the Russians spent billions of dollars creating an elaborate web of lies designed to cover it all up. The justice department guidelines require Mueller only to provide the Attorney General with the confidential report explaining decisions to pursue or decline prosecutions.
From there, Trump's hand-picked new Attorney General William Barr will decide what information to provide to Congress--and the American people--in his own written summary of the Mueller investigation. Barr could just hand Congress a single page with bullet-points.