Doesn't one generally prepare avocado toast by ... spreading avocado on toast? And maybe adding salt, pepper, and red pepper flakes, but that doesn't seem like particularly recent cultural knowledge - you do that to all sorts of foods. It's about as complicated as putting butter on toast.

The version I’ve been eating for a couple of decades goes like this:

Good bread is key, I like olive sourdough or something chewy with grain. Layer of avocado, layer of hummus, sprinkle feta cheese, sliced tomatoes, lettuce on the side as a “chaser” and... yum.

I guess that’s “cultural” in that it’s just adding avocado to a Greek thing. I’d guess that’s the story of how a lot of people got into various new produce... add it to the familiar.

It is easy to make an egg and cheese sandwich too, yet they don’t exist in every culture. Culture is knowing you can, and knowing when the details are “wrong”.

I don't think the avocado toast meme has spawned the popularity of avocados, but rather the other way around.

Avocados have become very popular in the low-carb/paleo/"health" community, alongside coconut oil, and various other trending foods.

I don't think that people have been lacking the knowledge to put avocado on toast until a meme about millennials never being able to buy a house due to spending too much money on avocado on toast.

They're also VERY popular for baby foods these days as well for the reasons you mentioned. Lots of people are trying to avoid too much sugar for their babies.

It's popular for baby foods for the same reasons that banana is - babies like it, it's fairly nutrient-dense, and it's soft so doesn't pose a large choking risk.

Exactly. Ask any quack chiropractor and he'll tell you about the "superfood" benefits of avocado.