Currently only two courses have more than 100 registered users.
A total of 19 courses are designed to teach Polish speakers selected words, sentences and expressions in Esperanto. 8 authors, 1 contributor and 1 complaint about language mistakes> Esperanto
List of courses:
- https://www.memrise.com/course/789081/personaj-pronomoj-eo-pl/ contains 7 words, 5 users, no one has used it for a month.
- Mazi en Gondolando 001 - Memrise contains 13 words, 3 users, no one has used it for a month.
- and 4. La Kunularo de L'Ringo - J.R.R. Tolkien - by Kondziuś - Memrise contains 22 words, 2 users.
- La Hobito aŭ tien kaj reen - vortoj por… - by tomaszym - Memrise contains 17 words, 3 users, no one has used it for a month.
- a large course La teorio Nakamura (kurs Lernu.net) - by yubizume - Memrise but only 6 users - it is worth to merge it with other users, e.g. merge it with course no. 10.
- Leaderboard - La hobito - by Dotevo - Memrise contains 208 words, 11 users, vocabulary from the book. It was worth to promote it
- Esperantaj vortoj por progresantoj - by tobiaszq - Memrise words 445, more advanced course, used this month
- the founder deleted the account Esperanto - by deactivated user - Memrise has 942 words, used this month.
- https://www.memrise.com/course/1157007/kurs-esperanto/ contains 2600 words, I am a contributor, more than 100 users
- https://www.memrise.com/course/342282/esperanto-metoda-bezposrednia/ contains 887 words, has 473 users
and courses 12-19.
which are different subject areas and could be integrated into a single course. Interest in these courses is currently 1 user per course.
Conclusions: it is worth taking care of courses no. 6, 7, 8, 9, 10, 11 and 12-19. This would result in a maximum of 7 courses of higher quality than the current 19 
and in case of interest you can gather the authors and contributors of these courses and create one official course 
( Translated with DeepL Translate: The world's most accurate translator because English isn’t my native language)