You can use one of the reporting forms linked at the top of the forum here. I think the Reporting Abuse form is the easier one to use, but since it isn’t actually abuse you are reporting, I would recommend using the one linked under Wayspot Removals.
Adding a link in case it doesn’t show for you: https://niantic.helpshift.com/hc/en/21-wayfarer/faq/4212-reporting-a-wayspot/?l=en&p=web
That one never matches what I am trying to report, but just pick something so you can get to the text box. Attach all the evidence you have as to why you believe this should be removed as a sensitive location. Not just that you can’t enter it.
You get an automated acknowledgement when you send the report. If that asks for your credentials as property owner, do not reply. A person will get back to you.
I do not know how they will decide on this. Removal criteria is internal, and does not match acceptance criteria. But you can make sure they are aware of the situation.
Adding a link to a statement about removal criteria: