A religion is just a meme that people take seriously.

There is a neat video from CGP Grey that discusses the infectious transmission of thoughts: Achoo!

I thought so, wasn't sure, was about to double check and then figured some wise soul in the comments would know. And here we are.

First time I ever encountered the word meme was in regards to religion.

In the original Dawkins sense, it’s a memeplex.

Exactly. Spreading and replicating like viruses across host bodies. And just like certain viruses, some can stay dormant for years, never fully going away - e.g. "The Game" (sorry not sorry). :p

Religious sects are just factions with differing headcanons about their religious text’s characters.

religion isn’t state-provided lol

I had both Dawkin's definition and internet memes in mind as I wrote this, since I don't think they're so different in the end. A meme (even in the modern sense) doesn't have to be a funny image: In can be a practice, like rickrolling; a text like copypastas, a story -true or fictional, like "operation baja-blast" or creepypastas. Some combine several of these things, like the meme "loss.jpg" contains the comic's story, it's pannels, and the behaviour of hiding the loss symbol or finding it. All of these things are also what religions are made off!