CF7 5.1 with v3 reCaptcha allowed so much spam through (hundreds of mails per day). A glimmer of hope was posted by the author of CF7 that 5.1.1 would make improvements. Well.. 5.1.1 blocked EVERY attempt including legitimate form posts and then that author blames theme creators for the problem. smh…(All mentioned above).
Just a follow up that I too, reinstalled CF7 5.0.2 and updated the keys back to v2 reCaptcha and all is working well. No spam, no intrusive Google badge at the bottom of every page, and legitimate message can now be sent once again.
Onward and upward in search of a new contact form plugin (free or not-free).