Well, sure, on a few of them. And then what? Could be quite a leap for single-celled organisms to evolve into something resembling a flying insect. Given how successful insects have been on our planet, why would life evolve into anything more complex?

I'm actually not too worried that we're the only example of life in the universe. Instead I'm more worried that the galaxy is filled with planets containing nothing but slime mold.

It would be pretty trippy to think about. A planet not unlike our own in terms of atmosphere, water content, temperature, etc, and it's all slime mold. Entire mountains, covered in mold. Rolling hills of mold. Valleys thick with mold. Mold everywhere.

Ours may very well be the only planet in the universe where life evolved to one day ponder the possibility of a universe filled with mold. Multiverses and Moldyverses.

So, who knows, we may take it upon ourselves to spread life and make the universe less moldy.