I would 100% leave.
I would also leave if my partner didn't want to have sex with me.
I hope in future that it becomes normalised for people to be honest and open when they know there is no chance of their sexual desire for their partner coming back.
I totally understand that people don't want to be honest as they are afraid of their family splitting up, but when a person isn't honest then they often end up in a situation where as you said they do it even if they don't want to, maybe it's only occasional, but that doesn't really matter because having sex you don't want to have can cause a lot of sexual trauma even if the person doesn't really understand that at the time.
There's a lot of talk on mumsnet all the time about coercive sex but it leaves out that whole other side of the dynamic and conversation.
Often one person (normally the man) is accused of being coercive but the woman is often giving lots of different reasons why she doesn't want to have sex, but unwilling to be completely honest and say that she doesn't want to have sex again.
All of the obligation and responsibility is put on the person who wants sex, to not put pressure on the other person, to accept it and so on and there is zero responsibility or obligation put on the other person to be honest....and when things are that way that doesn't really help anyone, coercive sex will still be a thing, people will still have sex they don't want to have.