That's hard fantasy. Soft fantasy can be good too.

Crap fantasy is still fantasy. Had a great time coming up with bad fantasy stories in my childhood when I knew nothing about good writing. Art is what you make it.

A clearer way to phrase it might be "there are no rules for the genre of fantasy". An individual world needs self-contained rules, yes, but just because Tolkien's Dwarves have beards regardless of gender doesn't mean that your Dwarves need to be the same.

To write good Fantasy (of SciFi), you have to go through a process called “World Building”

I think this is more implying that you don't have to work from the same framework for every fantasy world. Not everything has to be set in Arthurian Medieval Times with Crusader-Era social sensibilities. The menagerie of mythical creatures isn't a prerequisite or delimiter (dragons / unicorns / etc are not a requirement nor are robots / cthulhoid horrors / woolly mammoths disallowed). You need internal consistency (to a degree) but you aren't forced to adhere / omit any genre trope.

I would say, at an absolute bare minimum, you need some kind of fantastical or supernatural element to make it "Fantasy" as opposed to "Historical Fiction" or "Science Fiction" or some other category of fictional prose. Although, the genre of "Magical Realism" does make even that distinction a bit fuzzy.

many literature teachers / professors don’t even know about the idea of World Building

You don't necessary need to go through the whole work of World Building if you're just banging out a short story or novella. Even serial writers don't necessarily bother going deep on the background material until they feel the need to expand the scope of the setting. I mean, look at the Star Wars setting. George Lucas didn't have Jabba the Hutt defined as a big slug monster until the third movie. In the original film, there was a cut scene in which Han confronts Jabba, who was just a be-feathered chubby gangster.

If you're just spitballing or cranking out bits of fiction in brief, World Building can be superfluous. A story that takes place entirely in a single house over the course of a long weekend doesn't need the kind of scaffolding that a Long Walk to Mordor requires.

Toss a lighted match into the growing puddle.

Match goes out.

Nah this one is easy.

If it's green and sparkly, it's a good thing. If it's green and bubbly, it's a bad thing.

Or radiation perhaps?

Purple: Magic??

Green: Life/death??

Red: Life/fire??

Blue: Magic/cold??

Honestly the only colour I don't feel uncertain about is orange, that's always bad.

Also on the topic of health potions, a great piece of advice I once heard was that if your players are in a foreign land, remove health potions. Give them health biscuits and watch them reconcile with God.

FWIW, potions are drugs.

There is (was?) an electric power provider in Germany by the name of Yellow. Their whole marketing was "electricity is yellow!"

what do you mean? electricity is purple

the flask is green! i would know since i emptied it one too many times snd the texture is dark green

DM: Roll a Vibe Check

Player: I rolled Dark Green

DM: Ooohhh...

My vibe is slightly hurt with a hint of mental damage

Pixel dungeon does the same thing, you don't know when you start a run what any color potion does. So they're randomized.

The pulp is from fruit, right? The pulp is from fruit, right!?