Lady Bracknell has very conventional thoughts about love, engagement and marriage. She seeks an acceptable suitor for her daughter who can match Gwendolen in terms of wealth, social standing and family name. This means, of course, that Lady Bracknell isn't very impressed by protestations of love.
Gwendolen is completely unrealistic about love, engagement and marriage. Her greatest aspiration is to marry a man called Earnest because that name "inspires absolute confidence." This is ironic indeed considering that both Earnests in the play are falsely named Earnest.
Cecily Cardew is equally unrealistic about love, engagement and marriage except that Cecily takes a slightly different approach. She is secretly in love with Jack's rapscallion imaginary brother Earnest (of course, she doesn't know he is imaginary) and has great visions of reforming him and improving his life making him undyingly devoted to her.
Algernon sees no point in love, engagement and marriage, being appalled that Jack, who is Earnest in the city, wants to marry his cousin Gwendolen when jack can be so free and independent with no ties to bind him. Of course, this resistance changes when he assumes the identity of Jack's brother Earnest to go the country to meet Cecily and falls in love with her.
Jack, who it turns out is Algernon's elder brother--before he was lost in the handbag, anyway--is the only one who has a realistic view of love, engagement and marriage providing that the two people in question are in love and reasonably suited to each other in terms of wealth, social standing and family; the key word is "reasonably." Unfortunately, since he was found in a handbag, he can't claim a birth family, which is why Lady Bracknell refuses to give her consent to a marriage with Gwendolen. In the end, Jack's parentage is discovered to be that of Lady Bracknell's sister and General Earnest John Moncrieff, after whom Jack was originally named.