I think it's a scale based on what people like. Asking a partner/date to try and drizzle chocolate or spray whip cream on them during sexual act is definitely vanilla.
Asking them if they are ok to pour a 10 gal bucket of marshmallow fluff in bed and have sex in that is another and is not vanilla at all.
Most people on this forum would likely stick to the latter. But yeah your question seem antagonistic and tabloid-drama tone because at end of day, that statement can be said for any fetish/kink. Plus going to any enthusiast forum and asking "Is gardening really a big deal?" Or "Is BDSM really a big deal?" Just wrong way
Big deal: As much as any other kink for those that have them. But it is less know/accepted as other kinks so can feel like a big thing to open up about. Also more likely for ridicule as it's a little strange compared to BDSM.
What I call the gateway WAM, how you would introduce a new partner: you are right, it's not much. lots of baby oil, or foam, or eating food off each other. It's nothing. Similar to light spanking or fluffy handcuffs. But if I was to bring out my gunge tank on day one to someone tending more vanilla, then there would probably be issues.
This is certainly NOT a vanilla kink, it is not accepted yet as when it does appear on TV, it's always done in a slightly mocking tone at best. It is not well know outside of kink circles and many folks wouldn't even want to try it.
For us who have the kink though, it's just normal once we accept it.
I feel like a lot of people here treat WAM as if it's a massive deal, a big undertaking.
Realistically, getting a little shaving foam in your nostrils or chocolate sauce in your eyebrows is not a big deal.
Is WAM really that trangressive? I don't think so, to be honest.
Maybe people would like to believe its a big deal, but realistically it isn't.
Let's face it - most of the models who participate do not view it as risque.
Just an observation.
People can happily relax and view this as a very *vanilla* kink.
WAM, by itself, in isolation, unconnected to other kinks? Not that big of a deal.
Even if slapstick isn't part of your interest in the fetish, the fetish can easily be connected to slapstick moments in pop culture to help someone else get a good frame of reference. You don't need to step back and explain what a dunk tank is, or a pie in the face, or slime, and so on, whatever your tastes may be
Now, where it might become more/less of a big deal is where your specific tastes lie. I'm pretty vanilla. I like swimwear or scene-specific outfits, slime, chocolate, and pies in the face.
You could easily put someone on a game show, have them answer trivia questions, have them get a pie in the face for every question they get wrong/right, depending, and you have something totally innocuous. Ergo, not that big of a deal. Changing the outfit might make it more obviously fetish material, but even then, with swimwear, you don't have anything that the person wouldn't wear to the public beach/pool. So, I'm lucky that my interests are close enough to other people's frame of reference that even if it's not their thing, it's not so outlandish that they're generally not willing to give it a try.
But, other interests you might lay on top of the fetish or that might flavor the fetish might be a deal breaker or make it more of a big deal. Some folks like underwater breath play, or messy bondage, or feet/socks, or tickling, etc. Those aren't my thing, but if they're your thing, great! Those interests, overlapped with the fetish, might make it more of a big deal. Or less.
One of the first people I ever met online - a hawt goth chick who looked like Death, from the Sandman comics - was incredibly condescending towards what I was into because it wasn't the blood, bitey, more extreme side of BDSM that was her thing.
For a while, it kinda made me question where I was at and...
Yeah, the milder aspects do show up in everyday lovemaking and, no pun intended, water things down...
But really what happened to me was a bit of kink shaming, and it wasn't cool.
Also... vanilla (as in vanilla bean) is a really exotic, rich, and expensive flavor with a lot of depth to it that most people miss by partaking in watered down artificial versions of it that pale with the actual thing.
And also now I want to do something fun with a good vanilla milkshake.
How big a deal it is, or not, will depend on a whole host of factors and be different for every individual. It'll also depend on who they are sexually and what they ultimately want out of life.
Someone in a very conservative area, with a huge family and lots of close connections, in an area where everyone knows everyone else's business, traditional religion dominates, and any transgression from what's regarded as "normal" is savagely punished with ostracisation, loss of employment, and outcasting, will have a very different experience from someone more individial, living in a major cosmopolitan city, with an employer who couldn't care less what they get up to in their own time.
The biggest thing that seems to come up, or certainly used to, was straight guys worrying how they'd get a "wam girlfriend". The answer of course is that you don't get a wam girlfriend, you find a girlfriend who's willing to explore stuff together, including things sexual, and isn't phased by the impersonal nature of fetish sexuality. In the modern world where people of all genders are a lot more open about sex and kink than they once were, this is rather easier than it was 40 years ago.
TL;DR - it's going to vary massively from person to person.