You're right, luck is a huge aspect of natural selection. The fanciest new mutation is lost forever if the wrong sea turtle hatchling gets eaten by a gull while digging out of the sand. Them's the breaks. Evolution works on many faint parallel signals gradually accumulating over many generations in the middle of a raging luck storm.

The appendix is generally assumed be a vestigial structure, like wisdom teeth, ear muscles, and goosebumps. These things are on the way out, but not quite gone yet, because evolution is an ongoing process, both in acquiring and eliminating traits.

At a top speed of 40000 km/h, humans are the fastest of animals. Without the use of tools though, that honor goes to the peregrine falcon, which can go 320 km/h. But take these birds out of the sky and put them into an undersea coral reef and they won't do too well. The point is, for evolution, environment is everything.

Humans follow a completely different survival strategy from other creatures. Humans excel at thought, language, intricate hand manipulation, problem solving, knowledge accumulation, and above all adaptive social organization and cultural experimentation. Unfortunately, as with any processes, it's possible for these processes to become afflicted with pathologies, one of which is called religion, as you say.