Artsy is focussed on a specific niche in the art market that is not the high end (ie $100k ++ work), but more what they would call entry level $5k - $50k works. Artsy (and some of it's competitors) help these entry level collectors to get a greater survey of what is happening and what is available in the art world. To date, this would have required travel to galleries around the world (mainly NYC for the past couple of decades) and/or travelling to one of the big Art Fairs (see Art Basel - a one week extravaganza where more than a billion dollars of sales is likely). If you have the time and access to those events, you will get a great survey in a couple of days.
Artsy simply brings that to your device/home/computer. They don't make sales, more make the introductions to galleries that are selling the work. It continues the overall art market movement away from bricks and mortar 'galleries' to online and art fairs.
The value add (pain point) that Artsy provides is the recommendation engine. This is unique (not sure how well it works from my experience on the site) and is crucial in a market that is always looking for the 'new' and 'exciting'.
The overall market is terrifying in that million dollar plus works are traded over .jpg form. That's why there is a significant cohort of art consultants that are paid to look a work in real life to provide the '3D' context.