Its estimated that RouterOS is 30% of the global table as small operators around the world use Mikrotik for edge routing and have for the last 20 years.

Carrier grade service provider networking Mikrotik developed a decade ago. MPLS lets you stretch layer 2 around whatever obstacle you need to. It improves reliability and makes the network easier to manage.

Using ISIS as the IGP is is a high performance design choice for service provider and is required for redundancy. You can still use OSPF if you prefer, but ISIS scales better