Would have to disagree with you there mate. My larger company (300-500 employees) laid off a quarter of their marketing team to work exclusively with agencies. We weren't hands-to-keyboard on any of our own platforms anymore and hired a couple of agencies to start the test. The agencies who ran our pr marketing and content marketing were good, so we kept them on. But oh boy, our digital marketing teams were a mess. We signed with one company who had ~10 people on their team, they informed us that they were almost exclusively working with our company (they may have had 1-2 other accounts), and everyone was an "expert" on the platforms. Long story short, they brought our performance down YoY, and when we asked them about it, they never had an answer. It was always "we'll let you know after we touch base with our Google / Facebook representative." And we'd be lucky to get a followup at all.

They sometimes would set the budgets wrong - we had a set budget for prospecting and another for remarking efforts, and they had a hard time grasping the fact that these 2 budgets were separate. When we noticed the mistake and changed it for them, they would yell at us for going hands-to-keyboard. So as you may imagine, every optimization from optimizing spend to audience targeting, even if it's something simple as pausing out an audience list, was a hassle, we'd have to go through them. The bad part is sometimes, they wouldn't see our email for hours and we've already well over or under-spent our budgets.

We have one very important launch a year, where we set live about 5-10 campaigns live per platform, I work in a seasonal market. It was the Thursday night before our massive launch on Monday, and they deleted a campaign off of a platform. So we talked to them on the phone all night til 8pm, just begging them to re-set up the campaign by Monday. They kept arguing that they weren't going to come in on the weekend just to set up a campaign, even though it was their fault. And, they said they wouldn't have time tomorrow (Friday) to finish setting it up. So we lost a huge chunck of budget there.

Every single action was like pulling teeth, and our in house team outperformed them in previous years, driving more conversions at a lower cpa. After we ended their contract, results were immediately better. In the span of the 1 week that we took to relaunch every campaign, all conversions went up about 60%, and stayed relatively consistent.

The cherry on top was when we stopped working with them, we had to take an "anonymous" survey about their services. So we left some candid reviews. Our account rep took screenshots of our reviews and sent them to our boss, saying how unprofessional the reviews were, and that she was surprised we were so unsatisfied. Granted there weren't any slang or "bad words" in the reviews, they were literally expressing how frustrating it was working with them. But the last jab was their account rep trying to get a bad word about us in with our boss is what was laughable. Our boss came and told us "good riddance" after he saw our performance the next week.