You can definitely get this data, it's just a bit hidden away. Your assumption was right, it's one of the main reasons to use dynamic creative in the first place, to get some early learnings.
You need to go into your Ads Manager and select the specific ad. Then look for the "Breakdown" dropdown menu (it's usually near the top right of the reporting table).
Click that, and then select "By Dynamic Creative Asset". You'll get options to breakdown by:
-> Image, Video & Slideshow
-> Headline
-> Primary Text
-> Description
-> Call to Action
It'll show you the spend, results, CTR etc. for each individual part.
My only word of caution is don't treat this like a perfect scientific A/B test. The algorithm is going to push budget towards what it thinks will work, so some assets wont get a fair chance. What I'd do is use this data to spot the top 1-2 performing headlines and images, and then build a new, separate ad using just those winning combinations to really analyse their performance properly.
Hope that helps!
