How important is plot in erotica?

Yes the build up is v important

I think the characters have to be people I like and can relate to, otherwise I don't get turned on.

This is a link to a medical fetish story I wrote, there are more grouped on my profile if you like it.

https://similarworlds.com/fetish/5453325-A-Medical-fetish-story-This-is-a-medical-fetish-story-that

I think it is very different per reader, and that you can find audiences with various mixes.

What is it you wish to write? Do you want to tell a story that contains erotica or do you want the erotica to be the core essence of the writing? If you are doing a very short story, the latter might be easier. Start near the beginning of passion. A scene where they are kissing near the door without full introductions. Then a flashback to them meeting. Then clothing is coming off, then a flashback of growing interest or temptation, denied in the moment. Build the background into small flashes during the warm up to give it room and tease the reader along a little before the big scene.

Or not. Just brainstorming.

Without it, it gets old fast

It depends on your target audience. Write what you like and what interests you and go from there

to me extremely! no matter how silly or stupid i want a reason for the erotic stuff.

if it is just look they fucked i'm not interested.

same with fan service, ooh the sexy woman in the show is being sexy? who cares, is there a reason for her to be sexy or is it just eyecandy!?

I thought the plot was the point tbh

Very simple, do you enjoy foreplay? Or do you prefer just jumping right in and being over with it quickly? If the former, a good story incorporates the elements of foreplay in a reader's mind. Perhaps the stories you read were either too involved, or went right to the action and didn't value the rest.

Depends on what the reader wants. I think the reader wants some sort of background on why the people are having sex.

Without some character development .... background and familiarity .... it's just wham, bam

That's boring ....