...staffed with people that are political opponents of the person they were investigating...

Neutral career instigators are not "political opponents."
The only political elephant sitting in the living room is the AG, who submitted an unsolicited piece of legal gobbledygook asserting the silly proposition that no President could commit obstruction of justice.

Trump heard of Barr's belief and appointed Barr to be AG [along with the acquisition of the spineless GOP Senate].
Also, no, Barr is not stonewalling the release of the report.
He is taking the time to redact the parts of the report he is legally obligated to redact.
The only part his is legally required to redact is grand jury testimony, and even that can be waive with a court order. Even if grand jury testimony were to be redacted, that could be done in a couple of days.
Trump has explicitly waived executive privilege.

"Security concerns" are a red herring,

The report is to go to the OVERSIGHT committee, which handles confidential information all the time.
The only reason the redacting is taking so long is Barr is scrubbing it of all information harmful to Trump.
Just admit that you are just mad the report doesn't say what you wanted it to say and are now just grasping at any straw you can to avoid admitting that your hatred of Trump caused you to fall for a conspiracy theory that is just about as far-fetched as "Loose Change".
I would like some explanation of the 19 contacts by the Russians with the Trump campaign. I would like to know why Trump's people failed to report any of these soliciting of cooperation to legal authorities. I would like to know why, when these contacts came to light, Trump and his people lied about all of them.
My best guess about what happened is this: Mueller was tasked with finding conspiracy. Conspiracy requires agreement.

My best guess is that Mueller was unable to find evidence to prove beyond a reasonable doubt that Trump agreed to any of these 19 solicitations. But why do I have to guess?