We can detect water, and oxygen in the atmosphere using this method.
Plus we can estimate it's temperature based on it's orbit and star's energy.
If it is in the habitable zone we can only suspect that it potentially can support life, but we cannot detect if life exists there.
Well, even if we could do that we would get data from N years from the past, depending on the distance.
But we've detected life in volcanic vents, in arctic ice, in the upper atmosphere, in pretty much every niche on our own planet. Apparently life is pretty adaptable. So we have some clues already.
If we detect life on Mars or Europa it would likely be related to our own, so that's not an independent data point.
But if we detect that there's definitely life on a planet 3000 light years away, or if we exclude that possibility - that's a massive change in our model of universe, understanding of Fermi paradox and our origins.
Yes, I'd like to learn of life elsewhere. But life here is amazing too.
Can we detect if it has life without going there? Even just an yes/no answer would be immensely important.