People don't change. They don't get either better or worse as they grow up and grow old. They just get more like they were when their personalities had fully developed. Nature or nurture? A bit of each.
Would you ever dream of marrying someone who you believe will change for the better when the wedding is over? Of course you wouldn't, but many people do.
My friend Colin was an appalling snob, but he was universally liked - and even loved - by almost everyone he met, mainly because he acknowledged his snobbery as if it were a disease. He derived humour from recognising his condition for what it was - a harmless and silly set of prejudices which had been out of place since the days of his favourite author, P.G. Wodehouse.
He was of a particular class from a particular generation who professed to despise Germans ('Huns') and homosexuals, then found himself in later years with a gay German man as a very dear friend. He thought that was very ironic.
I have never met anyone who has contradicted my initial impressions gained within the first minute or two of meeting them, and I am not a particularly good judge of character. I think we all have an instinctive ability to accurately gauge the measure of someone at the first meeting, and we all have the same inability to hide our innermost selves from others.
It is just a question of who you choose to like and why you choose to like them. I like open, unguarded people who are not afraid of showing their true selves. I tend to dislike people who lack a sense of humour, but not always.
The widespread use of Tinder as a dating app makes me realise that arranged marriages are not as bad as I used to think they were. I know quite a few people who have met the love of their life through it.