I agree. Although a Grand Jury can question a witness, this is not at all the same as cross examination by an attorney for the accused. Furthermore, you made an excellent point when you said Obstruction was not proven. All that was offered in Mueller's report was evidence of obstruction that many attorneys considered strong and convincing evidence of Obstruction that, in their opinion, was enough to indict anyone other than the President.
We have built in safeguards for the accused in our democratic republic's System of Justice. So no matter how convincing and strong the evidence may appear, the charges are not proven until either the accused admits his guilt or the accused is found guilty in one of several types of hearings. Depending on the specific charges, the possible types of hearings include mostly procedures where the accused has an opportunity to question the evidence and to present his own witnesses and to cross examine the prosecutions witnesses either before a judge, or a judge and jury. In an Impeachment hearing the jury would be the Senate, the Prosecution would be the House, and the Judge would be the Chief Justice. However in an impeachment hearing, the accused can not be punished other than by removal from office .
Besides impeachment, the House has other ways of punishing those who interfere with its workings or desires under the Constitution. The House, according to Article One, or statute and established precedence, has the power to arrest and jail; to fine; the power of the purse, which may optionally be wielded against a recalcitrant President, Administrator, or judicial body; the power to impeach and try federal officers; the power to sanction and hold in contempt, and other powers as well.
The branches of the Federal government are not "co-equal" as is incorrectly and foolishly thought to be the case by many. Under the Constitution, and by intentional design of the Founders after long and arduous debate, the House was given power over both the Judiciary and the Executive Branch! It was argued by Hamilton that the most power in government should rest with the "people" and as the House was to be "the peoples' House"* the most power should be abide within the House. Hamilton's arguments eventually prevailed. And that is why the House is given it's three great powers: The power of the purse; the power to impeach on broad and undefined terms; and the power to specify to the Court which matters the Court may not hear. That these ultimate powers of the House are so little exercised is a curious, and perhaps unanticipated, result of the House so seldom being capable of acting "of one mind."
Currently there is the matter of certain individuals, including officers in the Executive Branch, having ignored House subpoenas. This is a matter that in the past has resulted in individuals being held in contempt of Congress -- not a matter to be taken lightly.
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*In Hamilton's era "the people" in the sense of the "peoples House" were male property owners and white with very few exceptions. Everyone else was disenfranchised.
