Bounce rate just means that someone came to your site and did not interact with the analytics DB in any other way. A user can scroll up and down 50x, stay until 29 minutes and 59 seconds, leave, and it will be a bounce. Bounce rate is a terrible leading KPI to look at. It's easy to understand and a classic vanity metric that doesn't matter. Applying an old favorite of mine: you can't pay your rent with a good bounce rate. Time on site is the same.

To combat this, you can set up scroll tracking. There are some GTM templates out there. Every time someone scrolls to a percentage of the whole of a page (for instance, 25% of the page but you can set it for pixels too), you can push data to the server. This artificially reduces bounce rate (yay?) but it gives you a much better idea of if people are actually getting anywhere in your content. It's actionable to know how far people are willing to scroll down your page.

Facebook Ads, like many platforms, have terrible placements by default that get mis-clicks that drive lots of clicks in the Facebook UI. Lots of these people click the back button before they even get to your site so analytics does not fire. A good example is an in-app ad where a user gets a reward for watching your ad. They may accidentally thumb it. Turn off all placements except Feed for FB & IG. These are the most expensive but the most reliable and highest quality for a small budget.

Ads are ruthless in the early stages unless you have a truly unique product/service and can run Google Ads. If I had a unique offering ("world's only data center ____ solution" then I would start there.

If you're a me-too company or just offering services, I would evaluate ads vs other channels like sales.