It is surely wrong to suggest that Austen presents Mrs Bennett as a sensible matchmaker, properly attentive to what is important in forming marriages.
Lizzy and Jane are hugely embarrassed by their mother's approach to matchmaking. Although they entirely expect her to be trying to make a match for them that is financially protective of the family, they are mortified by how wrongly she does this.
Like many other Austen characters Lizzy and Jane are quite clear that, alongside the economic imperatives that are central to marriage, there is also a positive duty (in the code of their gentry class, as conveyed by Austen) NOT to marry a man that you can't at the very least respect. Mrs Bennett simply fails to understand this duty.
Lizzy is extremely hot on the 'honour' of the gentry class. We see this most clearly in her delicious take-down of Lady Catherine de Bourgh, who, in her aristocratic vanity, disparages the untitled gentry. A large part of that honour revolves around the treasured fiction that money is less important than it really is. That's how the gentry distinguishes itself from 'trade' - the appalling 'new money' families.
So even when the need for financial security is desperate, it has to be pursued in accordance with certain caveats: You can't openly and nakedly offer up your daughters in return for wealth. You have to pay lip service (at the very least) to the idea that the marriage will allow your daughters to comply with the Church's requirement that they honour their husbands. And you have to pursue the marriage in a manner that makes it possible for everyone to pretend that money is not central.
Mrs Bennett is a clown and a liability to her daughters because she fails to see any of these niceties.