It does not matter where you advertise, as long as your spend is achieving your return on ad spend (ROAS) goals.
Facebook was the best game for a number of years because it was so cheap that it made the ROAS hurdle much lower. It is really simple arbitrage – buy low (the ads), sell high (your product).
But as expected, new ad platforms like Facebook that have good arbitrage, get crowded, and don’t work as well, or even not at all. So advertisers move on to the next new platform or often go back to old ad platforms that might have better arbitrage because they are less popular.