How is the dissolution of acetic acid that makes its aqueous solution a poor electrolyte?
There are two questions being asked here:

Why is aqueous acetic acid a weak electrolyte?

When acetic acid is dissolved in water there is an equilibrium reaction:
$$\ce{CH3COOH + H2O &lt;=&gt; CH3COO- + H3O+}$$

Since acetic acid is a weak acid, the equilibrium position lies well to the left, with only a small fraction of the acetic acid molecules reacting to form ethanoate and hydronium ions. The presence of this small amount of ions results in aqueous acetic acid being a weak electrolyte.

Why is acetic acid highly soluble in water?

Since the vast majority of acetic acid molecules do not dissociate when a sample is dissolved in water, the solubility has to do with the interactions between acetic acid molecules and water molecules. Water has a network of hydrogen bonds between molecules in its liquid phase and so when a substance dissolves in water this bonding is disrupted. However, acetic acid is able to form many new hydrogen bonds to water molecules and so this results in a highly favourable interaction, leading to the high solubility of acetic acid in water.