Let's put it this way. Imagine that the DOJ is one of the nation's largest law firms (spoiler: it actually is that thing).
For my entire life, it's been a very well-regarded and respected law firm. DOJ lawyers by and large knew their shit, and did good, skillful work. In the case of several divisions (e.g., antitrust), if one of your law school peers got a job there, you were as impressed as if they'd gotten hired on at one of the most prestigious private firms. And the DOJ's credibility wasn't in question. Yes, of course there were always individual lawyers here and there who weren't super great, and some that even may have played fast and loose with the truth, but they were outliers.
Now? That same law firm? It's name is mud. If you're a judge or opposing party, you need to assume that the DOJ team is potentially incompetent (depends on whether this is a low-level garden variety case, staffed by holdover career DOJ people -- in that case, you may be ok) and potentially dishonest. That is, when the DOJ is on the pleadings, you cannot assume they they will follow the obligation of candor to the tribunal.
It's actually fucking amazing to see an institution so completely wrecked so quickly. If I was in a hotly contested matter with the DOJ on the other side, and there was any issue on which the court should otherwise treat their representations as truthful, I would have a duty to remind the court that this entity has demonstrated that it does not respect the duty of candor, and has demonstrated so consistently. No representation they make should be trusted unless verified.
To a similar extent (although I have yet to see the lack of candor issue in any dramatic way), the same thing has happened with the Office of the Attorney General in Texas. At least the drumming out of competent people and replacing them with loyalists and true-believers in several divisions. Again, used to be one of the better, respected "law firms" around. And that reputation has taken a beating.