When routing is done in the spines (CRB model) a IREB must be configured at the spines.

Advertise Type 5 EVPN routes across the DCI: Type 5 EVPN routes are used for advertising IP prefixes between different data centers. These routes allow Layer 3 connectivity between the two data centers. By advertising Type 5 EVPN routes across the Data Center Interconnect (DCI), you can establish Layer 3 communication between the data centers.
Advertise Type 2 EVPN routes across the DCI: Type 2 EVPN routes are used for MAC address learning and distribution. These routes ensure Layer 2 connectivity between data centers, which is required to extend VLANs across the DCI and allow devices in one data center to communicate with devices in another data center at Layer 2.
Ensure border leaf nodes in each data center can exchange EVPN routes: The border leaf nodes are responsible for routing traffic between the data centers and ensuring that Layer 2 and Layer 3 connectivity is maintained. These nodes need to exchange EVPN routes to properly advertise MAC addresses (for Layer 2) and IP prefixes (for Layer 3) between the data centers.

You must have a DHCP server that provides the location of the software image and configuration files: This is necessary because DHCP is typically used in automated provisioning processes to provide the device with its IP address, gateway, and important information like the location of the configuration and software image files. These files are crucial for the device to properly boot and configure itself.
You must have a file server that stores software image and configuration files: A file server (usually TFTP or HTTP server) is required to store the necessary software image and configuration files for the Juniper device. These files are fetched during the provisioning process to set up the device.

An L3 interface (IRB) is required for each local VLAN: In symmetric IRB (Integrated Routing and Bridging) routing with EVPN Type 2 routes, an L3 interface (IRB) is needed for each VLAN in the local network. This interface provides the Layer 3 connectivity for the local VLANs and allows routing between bridged domains.
Symmetric routing requires MAC-VRF: Symmetric routing typically requires the use of MAC- VRF (MAC address VPN), which enables the device to route traffic while maintaining both Layer
2 and Layer 3 information. This ensures that both bridged and routed traffic are handled efficiently.
Symmetric routing requires an extra transit VNI for each VRF: It requires an extra transit VNI (a Layer 3 VNI) per VRF that carries routed (Layer 3) traffic across the VXLAN fabric.

You already have BGP multipath turned on (multiple-as;), so the control plane can install multiple equal-cost routes to the spines.
You also created a load-balance policy (load-balance per-packet;).
But the traffic is still not being balanced → because the policy is not applied anywhere.
In Junos, per-packet (or per-flow) load-balancing is not decided in BGP.
It's decided in the forwarding table (FIB) - the place where the actual packet forwarding happens.
That's why Juniper requires you to "attach" your load-balancing policy to the forwarding table.