I think it is important to remember the context in which P&P is set. It is set in the nineteenth century when women did not have many choices beyond marriage, they could not work other than as maids, teachers or governesses, and therefore the sole option for many women was to marry and have children. Women did not have the opportunies for education that they do today and although I am not trying to stick up for Mrs. Bennet (I think she is exceedingly silly) I can see how, based on this lack of opportunities, her nature is what it is: silly. Her life is occupied with matters of gossip and matchmaking and even if she did wish to do more she is constrained by the expectations placed upon women at the time. I would not say that the local mothers are boring people - they simply do not have much scope beyond trivial matters. However, Mrs. Bennet, ironically, is IMO sensible in wanting her daughters to find husbands with good incomes, for otherwise their futures will be bleak: "Single women have a dreadful propensity for being poor" wrote JA in a letter in March 1816.