I don't think it necessarily has to be surprising to be interesting. If it came from another solar system, it's traveled more than 4 light years (obviously much slower than light speed) to get here. That's a long time, and our solar system is a very small target, so the odds are (literally) astronomical.
There's a lot we don't know about the space between solar systems or the space outside of our own heliosphere. This is evidenced by our lack of understanding of when (or if) Voyager actually left our solar system. We just don't know enough to say. Having the opportunity to see something that came from outside our solar system is a good thing for science.
I was under the impression we did know that Voyager left our solar system -- could you clarify what you mean by this to someone not familiar with these concepts?
For several years there were a series of "voyager left the solar system today" headlines, each using a different definition of the solar system boundary because very little is known about where it is.
There's a lot we don't know about the space between solar systems or the space outside of our own heliosphere. This is evidenced by our lack of understanding of when (or if) Voyager actually left our solar system. We just don't know enough to say. Having the opportunity to see something that came from outside our solar system is a good thing for science.