Which is to say, two things are certainly true:

The universe is incredibly fantastically basically unimaginably vast. Practically countless (~10 million estimated) super-clusters of galaxies dot the heavens. There's just so many chances, so many opportunities, so much probability that, if you believe in life arising from a primordial soup, seem almost certain to be replicated.

Sometimes chaos, in it's fumbling teaming randomness, happens upon patterns. Patterns which sometimes stick, which sometimes reproduce, which sometimes grow. Entropy amid complex systems sometimes produces it's own enclaves of stability, sometimes.

The other true fact is that time is long and deep. Life on earth is not a flash in the pan, not an instant thing; it emerged slowly, over time, in differing waves, across time. The promise that life, once began, has a chance to ride these waves of time & to become significant, that it grows to fill rich biodiverse roles, grows to complete, that it thrives: if we believe in the soup of life, believe in the complex chemistries that powers cells, and believe in time, then a belief in other life seems not certain, but to me, highly highly probable.

Ultimately, the frequency at which abiogenesis occurs is 1/N.

It may be the case that N is small enough that the universe is positively teaming with life.

Or it may be the case that N is so unfathomably large that the odds are exceedingly small that abiogenesis occurs even once during the lifetime of the universe, and the universe just happened to get lucky.

But until we have some other confirmed, observed instance of abiogenesis, we can say nothing about N other than its lower bound is pretty large.

And I don't think we can pile probabilities on top of probabilities to say, "Well, we have no way of knowing how large N is, so I'm going to just bet that it's medium-sized."

[0] to the extent that events across vast spans of space can be said to be ordered

None of this is any kind of _hard_ proof of course, it's just attempting to reason through what we expect without having enough data to prove either way.

If we conclude for some reason that we are the first, with enough evidence, sure, like you say someone has to be first.

But with so little data, the priors for "are we first or are we just missing the others" just have to be tilted heavily away from "we're first".

Your perspective reminds me of the anthropic principle: https://en.wikipedia.org/wiki/Anthropic_principle

The popular conception is the "puddle analogy." You can imagine a rain puddle becoming conscious, seeing the intricacies of its perfect fit with the pavement that surrounds it and concluding "wow, this hole fits me SO perfectly, it must have been made for me."

Apart from cells, what are you referring to here? Especially, is there anything that can be considered "somewhat living" that is not a by-product of regular life, which as far as we know has only ever appeared (or thrived) once Earth's history?

We know of no other planet that has waterfalls.

Yet, because we have seen enough waterfalls on Earth we have an evidence-based scientific belief that waterfalls cannot be Earth-specific because all that is required for one: water, erosion, gravity -- exists throughout the cosmos in very large amounts.

Life is the same. We have seen enough of it in enough variety to know that it can take on many forms, including exotic forms that are impossible on Earth but would be possible elsewhere. The abundance of the ingredients and time are all that's required.

Furthermore, unlike waterfalls, we actually have no idea how life appeared and, despite trying for many years, have been entirely unable to produce life from non-living things, and we have never observed this process occurring naturally either.

Furthermore, every living thing we've ever looked at has been a relative of other living things - as far as we've been able to determine, all of the life on Earth has a single origin, a single original RNA/DNA code which must have been present in a single population of organisms, at a single location. This is a strong suggestion that the conditions that allowed life to appear on Earth may have been extraordinarily specific - otherwise, we would expect many unrelated beings sharing the planet (or at least it means that a particular for of life was overwhelmingly more adaptive and entirely wiped out all of the others).

Even worse, there is another phenomenon for which we only have evidence of one instance happening in the history of the Earth: all eukaryotic life has a single common ancestor, and there are no complex multicellular organisms which are not eukaryotes.

So, not only did life arise only once on the one planet we know it can thrive in, but complex life only arose once from simpler life.

So, while we can't say that it's plausible life will never again arise in the universe, we can say that for any particular moment of time, it is plausible that no new life is being formed anywhere else in the universe.

As far as we know all life is related and has the same ancestor. Even on earth the emergence of life seems to be a freak accident.

However, for structures where we have no idea of the process by which they are formed (like cells), we can't have any opinion on how likely they are to happen elsewhere, unless we see more examples.

What forms of life that are impossible on earth do we know about?

But life capable of communicating across space didn't arrive until 4.5 billions years and after several mass extinctions. Even on a cosmic scale that's a very long time.