So, why don't we still have dinosaurs?
> "Most of the building blocks we have looked at in other planetary systems have a composition broadly similar to that of the Earth"
If being "earthlike" was enough, this planet would continually be spawning life, as it originally formed. Those "respawns" would then start their own path of evolution. So as well as having us, the result of billions of years of evolution from the first time that life appeared, there would also be forms of plants, animals and all the rest that are the product of evolution from the second time that life started on Earth. And from the third, fourth, the seventy-seventh, the 2,916'th and so on.
But we don't. We only have a single thread of evolution that seems to go back to the start.
So it would seem that being "earthlike" is not a good idea for a planet if it wants to start producing life. It is only a hospitable environment for once life has got past the initial stages. After that, being earthlike is not a set of conditions that is suitable for starting evolution.
The conclusion would be that a planet only has one shot at starting to give rise to life-forms. Maybe once they get to the stage of converting methane, CO2 and ammonia into an environment rich in water and oxygen, they have past the point of spontaneously allowing life to form. If whatever life had developed, then died out, it would explain why we don't see other planets' TV.
The trick wouldn't be starting life, but in having the remarkable set of coincidences, luck, and starting conditions to allow life to avoid all the extinction possibilities in the billions of years after it forms, to eventually give rise to intelligence. Or us!