There are billions of stars in a galaxy, and billions of galaxies in the known universe. There could be more worlds with life similar to ours than there are grains of sand on Earth's beaches, and drops of water in its oceans, and we could still never even be aware of them simply because the universe is that vast.

Precisely the opposite. There are so many possible world that match all the criteria (that we know of) for life just within our galaxy, that we should detect some of them. Our solar system is pretty young compared to the age of the galaxy (4B years old vs 13B years old). Imagine a civilization identical to ours, but that would have appeared a mere 1 billion years before us, not only radio signals should be detectable (because the galaxy is just 100k light years across), but a civilization similar to ours, with 1B more year to develop technologically should have easily been able to send probes, at the very least, all over the galaxy (see von neuman probes) so we should also see that, and yet we don't.

And this just assuming a single civilization, while as you said: there could be more worlds with life similar to ours that there are grains of sand on Earth. So where is everyone?

Detect with what? We've had radio signals for about a century or so and our signals have barely made out of the solar system at which point it's just background noise. We just barely can detect planets and only in optimal conditions. Our tech for all extra terrestrial purposes is laughably primitive.

You greatly overestimate the size of the solar system. Our solar system is a mere ~20 light hours in radius. We even have two man made objects out of the solar system (Voyager 1 and 2). In a century, our signals already made it past ~15 thousands star systems.

So now imagine a civilization similar to us but slightly older, not only would this civilization's signals have reached all parts of our galaxy, but those signals would likely be much stronger than we have produced in the last 100 years. It would also be possible for a civilization a few hundred millions years older than us to send probes to every star of the galaxy by now.

"there is still no good explanation for why Earth would be the only place suitable for life forms similar to us"

1. There is still no good explanation _that we know of_. We don't even know if we are the only life forms in existence or not: none of the observations made so far support the latter, but do not disprove it either. So we can't prove or disprove _any_ hypothesis about extraterrestrial life.

2. "Suitable for life similar to us" and "suitable for life to spontaneously appear" are two very different things. And we still don't know enough about either.

Maybe because worlds are continuously created and destroyed, so they have no time to create life and then develop technological civilization. We are just lucky to fit tight limit.

That is pretty much the 'great filter' solution to Fermi paradox: there exist some kind of filter that prevents most life forms from being galaxy-spanning where they would be easily detectable.