The point of Author Austen having Anne dislike Mr. Elliot's outward correctness is not that 'no one can be universally liked.'

It is that if you can not see below the surface, whether it is reserve that prevents you, or suave flattery, you can not know what sort of person another is.

There are many characters in Austen's novels that are generally liked, and genuinely good. Jane Bennet, Elinor Dashwood, Col. Brandon, Charles Bingley, Mr. Knightley, Henry Tilney, Sir William Lucas...

Mr. Elliot is to be distrusted because Anne has never seen him react in an unguarded way: Mr. Elliot was rational, discreet, polished, but he was not open. There was never any burst of feeling, any warmth of indignation or delight, at the evil or good of others. [...] She felt that she could so much more depend upon the sincerity of those who sometimes looked or said a careless or a hasty thing, than of those whose presence of mind never varied, whose tongue never slipped. (ch. 17)