I think the three main sonic limitations of the cassette source format are often noise levels together with high frequency response and sometimes dynamic range.
That aside, I still have many cassette tapes still I recorded on various decks in my various system variations over the years. Despite the age of some (30 years old in some cases) when I play these on my current system, by far the best I have owned I would say, they still sound pretty good. I even have some tracks on my music server I digitized from these cassette sources. When these come up in random play mode among others, they sound quite listenable, but I do not think I have any trouble identifying that these were sourced from cassette tape, mainly due to noise levels and frequency response. For other tracks that are more pure digital source or even vinyl, it is hard, although surface noise from vinyl when present is a dead giveaway.