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.
It takes people about a month to work through a language track, learn the language, and get on with their life. So I wouldn't expect to have more than 45k MAU. 70k MAU is because people LIKE the site and come back to learn another language.
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 there is nobody using your service for more than half a month (at that point they would mostly already be counted for 2 months) almost nobody will ever pay. What is your day 7, day 30 and/or day90 retention?
If is low all you can do is lower costs, which should also be straightforward.
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.