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Meraki calling the routers "Security Routers" is a bit misleading as they only work as a basic NAT/stateful firewall. They don't appear to do any actual traffic inspection or IDS/IPS or anything along those lines. They don't even block ALL incoming requests from the internet (you'll notice you can ping your public from literally anywhere), so it's happy to advertise its presence to the internet, something even your basic ISP's router will not do.
They do offer an outbound DNS based security solution, but that's something you could apply to any other router which allows you to set your external DNS.
If you look at the feature set of the Meraki Go routers vs something like Ubiquiti's USG series, there's a MASSIVE difference.