As for indolence, that would be ridiculous, but there are other interesting things.
What does this mean? I'm especially interested in what the "but" means here.
But is the ordinary conjunction here, signalling that what follows denies or qualifies what has just been said.
Reverting to the topic of marriage: it would of course be silly for them to marry. However, men and women may enter into other sorts of firm relationship which are more interesting.
You use the word
but when you already told enough pleasant things to the listener and you finally decide state what really matters.