Besides, aren't all nodes basically a gateway? Ie, a gateway is effectively just a readonly node on an accessible IP. Any node could be this if not bound the local net.
sure, but practically probably not, because you would need a domain and a easy way to update it + a cert + thats assuming you are not behind some sort of a NAT and have your own IP.
You don't need a certificate and a domain to run a gateway. For a public gateway, sure, that's desirable (though not strictly required), but for a private gateway (that most nodes are probably running anyway) you really don't need any of that. At home I can just go to http://localhost:[someport]/ipfs/[somehash]. With browser plugins you can also translate ipfs.io gateway URLs to your local gateway.
Well I was replying in the context of someone saying there is a meaningful difference to a gateway vs a node. If you access content via a gateway, your content is hosted by IPFS. The content gains all the benefits of IPFS, but you, the viewer, do not. However, if the IPFS Gateway works, ie it isn't throttling/blocked/etc, then you still get the content. I'm struggling to find a meaningful difference, is what I mean.
Now if everyone accessed the content via a gateway, then sure - that undermines the point of IPFS. But a gateway isn't inherently bad, nor is it worse in most respects than a local node - at least, to my understanding.