It does have 8x 10GbE ports and one of those can service as much traffic as the device can process.
I'd think they are more there for choice and HA setup. i.e. you'd use maybe 4-6 of the LAN ports, 2 for the LAN and pairs for DMZs. If the rest of your infrastructure uses SFP+, use those; SFP, use those; RJ-45, use that bank of ports
I wonder how Cisco Meraki can implement LACP on MX series router, when enterprise grade networks relay on high availability requirements.
Two switches (Stacked or vPC) share the same connectivity and availability, but have only one Uplink to the WAN devices.
Connecting a second interface Spanning-Tree has to have a Alt Block port of any kind in order to prevent loops.
Failover times are up to 35sec (RSTP on normal circumstances) and troubleshooting easy.
This is a perfect enterprise level SD-WAN solution, with a little bit of salt.
I hope Meraki will address this issue and perhaps some OSPF timer inconsistence as well.
Remark: LACP does only increase bandwidth when proper hash method (Src. & Dst. Mac's) is distributed.
Typically "Src. & Dst. Mac's" would not increase the bandwidth as one is the MX, the other is the core-switch and only one link would be used. The better would be Src/Dst-IP or Full Flow.