It's all a matter of degree. There is a continuum between vanilla and hard core kink and B&D and S&M and medical fetishes.
Vanilla sex is primarily vaginal sex and oral sex in just about any position they can achieve. Playful rape, not forceful rape or rough sex could also fit in.
A vanilla person might go for anal finger insertions, but probably not more.
A vanilla person might let their partner give them a few swats, but not a blistering, black and blue mark spanking,
a vanilla person might let you see them urinating on the toilet, but not watch them defecate into a bedpan after an enema,
a vanilla person might let you "tie their wrists" with a scarf, but not let you forceably restrain them with leather, rope and chain,
a vanilla person might let you pinch their nipples when they have an orgasm, but not allow you to use nipple clamps with weights attached,
a vanilla person might let you use a flashlight to look at their genitals, but not allow you to use a speculum,
a vanilla person might allow you to give them an enema if they are sick, but not for play or punishment,
etc.
Oral sex is completely mainstream except for really hung up or truly biblically religious people (not religious hypocrites like priests who fuck young boys), anal sex is not.
A measure I use for vanilla versus kinky is whether or not you could discuss your proclivities with your vanilla friends and relatives.