ReCAPTCHA is an often requested feature that we don't have Core support for and we should to reduce credit card testing and provide support with an easy was to recommend fraud prevention.
Stripe also emails us about implementing it when the detect one of our customers are experiencing card testing.
Note: We already have code implementing ReCAPTCHA on the "Access Control" tab so some logic already exists in the plugin to implement this, just not on the donation form itself.
We should also consider supporting reCAPTCHA v3 since it is less invasive than v2.