I'd say the Gateway also does load balancing, actively checks if the target is still online. And possibly works seemless together with other Gateways, for example for rate limiting you might need several nodes to combine their metrics.

We use Kong open source gateway. Anything they had in version 0.9 was sufficient for our use case but they're a VC funded company so they keep adding more features, especially enterprise features (ignore the AI stuff in the latest version). Configuration can now be in a database, or in files, or updated via an API.