In the past, my email got blacklisted because someone accidentally put my message in the spam folder instead of the trash. The difficulty in restoring your credibility is quite significant.

Being protected against spoofing is essential today, and DMARC is the recognized protocol to do that, almost everybody adopts it. I suspect that most email users do not ever know what DMARC is. The only thing that they understand is that if a message is suspect it is better to trash it. So, if you care about your email reputation, you shall periodically check it. In general, we forget to undertake periodic tasks.

DMARC Report accomplishes that and pays for itself right away. First of all, ity checks if you are DMARC compliant then, in case of issue it reports them to you.

I will honestly admit two things.

I'm thankful I didn't see the alert in action since I'm following the rules, but I trust it works (and hope never get an alert).
My DMARC record wasn't set up by DMARC-Report. It was done by a different email company from Appsumo that gave the right DNS record content. So it was already OK, and the DMARC-report simply stated "Compliant". It's anyway easy to find out how to set up a DMARC record by googling, even if you aren't an expert.