In OpenVPN, we use pushing routes extensively.
Main OpenVPN server works under debian and configures routes via CCD (push route).
On the client side, approximately 300 MikroTiks are running, and approximately 300 routes are pushed.
In recent versions of RouterOS (higher than 7.16), we've noticed a significant limitation on the number of routes the server can push (limited to approximately 30). Several clients (with the most pushed routes) after upgrade hang on the "Connection established" message. This error is architecture and network-independent.
According this post Pushing routes OpenVPN in ROS 7.14 version pushing routes are implemented on mikrotik’s OpenVPN server implementation but limited to 1400 bytes. Perhaps this limit is also now for client too?
Below is the same configuration on the same machine with different versions of ROS:
