Look at "gå på X" as a set expression which means go to.
Vi går på restaurang - We go to a restaurant
Vi går på bio - We go to the cinema
Vi går på kafé - We go to a café
Note that "gå på" only works with certain locations like those above. It is usually some sort of leisure activity. But you could for example NOT say "Vi går på skola" (school) or "Vi går på sjukhus" (hospital) NOTE THAT THESE ARE NOT CORRECT.
When you say "gå till" you emphasize that you are walking somewhere.
Vi går till restaurangen - We walk to the restaurant
Vi går till bion - We walk to the cinema
Vi går till kaféet - We walk to the café
In this case it is no set expression. It is just a normal sentence made up of the verb "gå" - Walk, and "till - to". Therefore it would work with other places too, such as hospitals or schools.
Vi går till en restaurang or even more idiomatic, to catch the continuous: Vi är på väg till en restaurang. gå på restaurang is a general activity, it doesn't matter which restaurant you're going to, maybe you don't even know yet. går till en restaurang means you're on your way to one specific restaurant.
That would indeed also be "we go to a restaurant", so it works for the reverse translation. But they mean different things in Swedish - åker till is talking about the travelling, while gå på is not.
For instance, gå på bio functions similarly to "catch a movie", sense-wise.
This reminds me of some similarly arbitrary-seeming English constructions/omissions. Sometimes when the location implies a general activity, the article is omitted (we go into town/to market/to work), and likewise one may find oneself "on" rather than "in" a dynamic or process-oriented location (on the psychiatric ward, on the bus, on the plane, on the way). There's some contention regarding "going to hospital" which seems to be more common in the UK; but they also say "disorientated" over there, and so invite grammatical mistrust.