I assume this is like pop-up blocking. You need to be able to open app store links some times (to get to the store to buy something), but you shouldn't be pushed there. But just like pop-ups, there is a big incentive for scummy advertisers to find ways around it.
I've reported this kind of thing to better websites (ones I knew/trusted) when it happened and they fixed it. I don't know if this site is fine with this or is just the victim of a terrible ad network.
It seems like it would be easy for Apple to add a confirmation like "Open in App Store?" Just like clicking on a phone number and have a confirmation before it starts dialing. Perhaps it's advantageous for Apple to keep it as-is, though?
In the meantime, I just let the advertisers know my feelings with a 1-star review. If everybody did that it would probably put an end to these pop-ups, but I won't hold my breath.
I've reported this kind of thing to better websites (ones I knew/trusted) when it happened and they fixed it. I don't know if this site is fine with this or is just the victim of a terrible ad network.