Having the elements of life means little if the conditions aren't right for it. Mercury just couldn't support life, it doesn't even have an atmosphere. What would it breathe? what would protect it from the intense radiation, the freezing night temperatures and boiling day temperatures (maybe not the latter as those areas are always in the dark)
You'd have better luck on Jupiter's Moon Europa, which is frozen on the outside but potentially warm deeper down due to its core being constantly stimulated by the gravity of Jupiter. It is likely one big sphere of water below all that ice, which a rather small rocky centre compared to how big the water and ice make it seems from the outside. And if you could warm up Saturn's moon Titan to a comfortable temperature - that would be the best candidate of all. Mercury would be too much effort to keep anything alive there. Only value it would have to us in the future would be a mining resource
I amazingly must have done so already - the Wikipedia link showed up purple when I googled them Maybe we've talked about these "water bears" before
Still, while finding even just a micro-organism on another planet (one that's alive) would be a huge deal, I think what people generally hope for is something a little more complex, even just a jellyfish-like creature or something we can "see" Maybe Tardigrades could evolve into something greater once introduced to a new environment though. It was micro-organisms that were the first helpers into making Earth suitable for larger, more complex lifeforms down the track
It's intriguing, especially on Mercury. We know that the universe creates DNA components on a massive scale in some nebulae, and Titan has a material in its atmosphere that was duplicated when researchers tried adding its atmospheric components to a sealed jar and stimulating them for a few weeks with electricity: amino acids. I will follow this story with great interest.
You might be right...or way off. Who can tell with extraterrestrial material? The beautiful part is that even on Earth, we have a huge variety of lifeforms, as you note, so we will probably be shocked by the form they take elsewhere. What a wonderful time to be alive!