I unfortunately watched first-hand a company come up with a mediocre "app" that had barely any content. Think short-form content and random videos moderately glued to some topic written by a bunch of low-wage "content writers".
This company then picked a biggish ad-spend budget, spent it on Google, FB and other ad companies (digital agencies). And the users just started rolling in over the course of months. The increase in users, let them "monetize" by convincing "sponsors" to "pay" for content on this new "platform", which netted them a big chunk of profit and more money for more ad-spend which made more users come.
Next up, they will brand and sell this platform which has "X-millions of users", even though most are one-off users, barely any repeat or long-term users, etc.
It's like some sort of endless shit-peddling cycle driven by marketing, and it was frankly disgusting to watch from the sides. Their stated goal was actually noble, uplifting, etc. But all they ended up doing was building a "herd" of users that they could monetize and use for marketing other projects, and helped no one except for their global brand, and their owners.
Sorry about the rant.
In summary: Yes, just get an ad-agency and pay them to help you get users. At least you have a valid product I assume and genuine value to provide in exchange for money.