Why is that depressing? It's not like we would actually be ALONE. We have each other. We don't need Vulcans or whatever else to keep us company and suck up our resources.

When you put it that way, it doesn't actually matter. There's always going to be someone competing for resources. The only difference is whether they have hands or tentacles.

Another potential difference might be diet. Perhaps this other, tentacled species can't resist the taste of homo sapiens.

Nope, still true with us alone.