That’s a figurative sentence:

Les rideaux ne veulent pas de certaines gens

Il y a des gens dont les rideaux ne veulent pas

meaning:

There are people "rejected" by curtains.

i.e.

Curtains do not want some kind of people.

Of course, this is stylistic as usually, people choose their curtains, not the other way around.

The last sentence means:

We are still missing curtains.

“Dont” means ” desquels” , ” duquel” , ” de laquelle”.

Here : il y a des gens desquels les rideaux ne veulent pas.

But ” dont” is more elegant.

Maybe one could explain the sentence in this way : ” there are poeple such that curtains do not want of them”, ” people whereof curtains do not want”.