Then you have nothing to complain about
I'm not complaining. Impeached Trump got himself impeached, among other reasons, for blocking some folks from testifying who were subpoenaed. What I did say is there is no reason for the Senate to not subpoena them as well. They won't because they're interested in protecting Trump, not getting to the truth.
Exerting executive privilege is not a crime or an impeachable offense
There's nothing to show Bolton, Mulvaney, et al., are entitled to Executive Privilege. The Supreme Court has ruled the Congress has subpoena powers for investigations. And recently, a federal court declared McGahn was not shielded by Executive Privilege...
On Monday, a federal district court did just that, categorically rejecting President Trump’s claims and finding that McGahn had a duty to comply with the Judiciary committee’s subpoena and to appear before Congress to testify. “[T]he President does not have (and, thus, cannot lawfully assert) the power to prevent his current and former senior-level aides from responding to congressional subpoenas.”