What I know is, while ago, there were lot of INFRA level issues.
When I contacted Mendix support, the response was, the usage of Mendix cloud increased thus slowing down the deployment process.
Unfortunately, the issue is still not resolved for us too. The ticket is still in progress.
Last week I got some response for the ticket stating, the resolution is further delayed.
For us, the project package building and deployment takes more than an hour.
Best bet is contact Mendix support, if you have paid cloud nodes.