You don't need a word for non kinky sex, it's just sex
No it isn't. That implies that there is only one 'normal', which is a very small range of sexual activity that you happen to like, and that everything else is essentially deviant. But that isn't the case. You don't get to arbitrate on that.
It's a bit like saying 'It's OK for gay/lesbian people to be described as gay/lesbian, but I don't want to be described as a 'straight' person because a straight person is just a normal person' or 'A non-disabled person shouldn't be called able-bodied because that's just the norm'.
Non-kinky sex isn't 'just sex', it's a certain form of sex that doesn't involve things that you don't like. You can't just decide that your preferences are the default and therefore don't ever need to be described.
It implies there is another kind of sex that you are denying your partner.
No, it implies there is another kind of sex, which there is. It doesn't imply you are denying your partner anything. It simply defines the type of sex some people happen to prefer, and are perfectly entitled to prefer.
I'll believe that it's not sexist when I see men who don't want to be pegged labelled 'vanilla'
The term 'vanilla' gets used for men all the time. Men are no more likely to be into BDSM than women. The mismatch in sexual interests that the OP describes happens both ways. Plenty of women like (for example) dominating or being dominated and find that their male partner isn't keen on that. Of course men find themselves having to justify their boundaries. But in any case, simply describing a preference as 'vanilla' doesn't imply it requires justification anyway. It's simply a descriptor. It doesn't have to be justified. Expressing a boundary doesn't automatically equal being forced to justify it.
It is clearly used and felt as pressure and criticism by women - I have felt this as have others
You can feel however you want, but that doesn't make the word invalid. Any perfectly valid and neutral descriptor can be used to criticise someone; that doesn't mean the word itself is the problem.
I've had people use the following terms used in a very negative, angry way to criticise me:
Feminist
British
English
Lefty
Liberal
Socialist
Vaccinated
Middle-aged
None of those things are bad things, unless you happen to be personally opposed to them. And they're also all perfectly true ways to describe me. The fact that they can be used as criticisms by unpleasant people who don't like those things doesn't mean that the words themselves are negative or offensive. They're neutral descriptors. Some people might well use them as insults (as people have done towards me) or feel insulted by them (if they were vehemently against those things). But that doesn't mean there's actually anything wrong with them or that they are intrinsically insulting words. Everything has a context.