Some communities are determined to recruit more members than they can handle.
This causes a problem, there is too much activity. There are too many posts to check, too many questions to answer, too many disputes to resolve. The important tasks get left behind and the entire community suffers.
The solution is to close the doors. Stop letting members join until you can support more.
A nightclub can be full, so can your neighborhood. Most businesses have a limit on the number of customers they can handle at a given time.
The same is true for a community. If you can only support 5000 active members, why would you continue to recruit more? It will hurt the community.
Close the entry and introduce a waiting list. Both newcomers and existing members will appreciate the community more.
Focus on the tasks that develop the community. Don't recruit more members than you can handle. It wont do you or your community good.