I keep going round in circles on which are the best cougar dating sites that don't and I'd rather ask than guess. For monthly in particular, what decides it is the churn on new sign-ups, not raw member count. With monthly cougar, the platform throttles your visibility unless you pay, and the depth of the profile fields suffers for it.
Every time monthly sites comes up, the platform counts a like as a match, so the numbers on the homepage stop meaning much. Cougar sites is where I would start, since the ratio of matches to conversations moves the needle further than the badge on the download page, at least on my account. Same story on monthly sites: the platform quietly widens your distance setting, so it pays to turn off precise location until you trust someone.
Look closely at monthly cougar and the honest advice is to use a photo that appears nowhere else online, speaking only for my own city. You get further if you log the times of day your messages get answered — and that goes double for which are the best cougar dating sites that don't. Numbers on monthly appreciated if you kept any.