There is no doubt that any form of jointing in a doll is a bit of a compromise - you usually have to sacrifice some of the sculptural purity of your piece to achieve that joint mobility.
Of course, you can completely avoid the problem by completely avoiding any form of jointing, but it could be argued that a fixed figure is more a piece a sculpture than a doll ("doll" to many people implies a degree of interactivity and it is hard to interact with a rigid piece of sculpture, but that is an argument for another day. Suffice it to say that some things occupy a space somewhere between "doll" and "sculpture".)
Fixed figure - is it a doll?
You can create successful joints quite simply by sewing hinges into your fabric limbs like this:
Simple hinge joints - dolls can be very posable
Sometimes I like to create dolls with disc jointed hips and thread jointed shoulders:
And neck joints:
Sometimes I experiment with knee joints, which require a bit of forethought to be successfully executed in fabric.
Some people are complete masters of the jointing problem - I'm thinking of those patient people who spend months making a BJD (ball jointed doll) with up to fifteen joints all strung together with elastic for total posability.....I'm in awe of that prodigious achievement! Maybe when I have a lot of spare time I might have a go at making one myself!