Years ago, Facebook advertisers had to follow a 20-percent text in images rule. A grid tool was used to determine whether the image would pass. Ads would get rejected due to too much text.
After that, Facebook moved to a sliding scale. You could still generally get your ad shown, but it may get less distribution if your ad image had a lot of text in it.
But, now? You may not even realize it, but there's no rule. In fact, most mentions of text in Meta documentation have been removed.