A credit card signup bonus is a one-off.

If you are staying at Marriott during promos, collecting one or more amenity bonuses per week, etc. you are going to rack up far more than 65k points from 39 paid nights. Stay at any hotel chain for a month-long stay during the times of year when there is no promo - especially at a CY with few Platinum benefits - the joke is basically on you...

Marriott has its issues and I'm not that big of a fan, but the standard earn/burn ratio is pretty good compared to the competition. It's promos that can move the needle...