Why can't the Xiaomi Wi-Fi Range Extender AX1500 form a Mesh network with the Mi Router AX1800?

The Xiaomi Wi-Fi Range Extender AX1500 cannot form a Mesh network with the Mi Router AX1800 because they belong to different generations of Xiaomi Mesh systems.
The Mi Router AX1800 is part of the first-generation Mesh architecture, while the Xiaomi Wi-Fi Range Extender AX1500 is designed based on a newer, second-generation Mesh system. Due to differences in underlying protocols, coordination mechanisms, and firmware design, these two generations are not compatible for cross-generation Mesh networking. As a result, they cannot be paired to create a unified Mesh network, even though both devices individually support Mesh functionality within their respective ecosystems.
For a stable Mesh setup, it is recommended to use devices from the same generation and product series. This ensures full compatibility, seamless roaming, and optimal network performance across all connected nodes.