Why are all gym memberships like this? The first thing I check before starting a service is how easy it is to end it. I’ve not been able to find a single gym with reasonable terms.
I do the same. So many gyms have abusive terms which is an immediate deal breaker for me.
There are handful I've found that aren't bad offering true month-to-month service. Give notice by phone or email by X day of the month and your membership ends at the end of that month. Miss that date? You only have one more month beyond that then.
For years Planet Fitness had a good deal they'd only run for a couple of days a year where you could prepay for the entire year for $99 (or later $120). You didn't give them your bank info, no "credit card on file". You could literally hand them the cash and 365 days from that day your membership would expire with zero action on our part. That was the best membership deal I've seen yet. I don't know if they still do that.
In the meantime, one could always pay with a prepaid card and then just never add funds when you decide to quit. Then just “return to sender” any mail they try to send you.
If you're using your real name I would imagine they'd send the debt to collections which would cost you even more when your credit score tanks and you try to buy a car or house.