At 1.500 signups per day (45K a month) 70,000 MAU are horrible retention. Usually you need about 10 times MAU to signups. Unless you can make that happen you have nothing that people actually use and not just try out.
We're not trying to be some business that sucks people into using our site every day and monetise them. We're aiming to teach people effectively and efficiently and then get them moving on with their lives.
We could make the site less efficient, or change it's purpose, but that's not the mission of the organisation.
If is low all you can do is lower costs, which should also be straightforward.