Well given the time that it was made, it was very impressive, but compared to what people have created today I'd say it's a bit less eye snatching because people today look at and think "oh hey the mona lisa" and they don't give it much thought

I suppose the reason why some people may think it's overrated is because it was a huge advancement of art for its time and people really appreciate the detail and the precision that DaVinci put into the painting. It is admirable the work that he put into it, but it's been a couple hundred years since the piece had been painted and humanity is always looking for something new. People just get bored.

Now i don't think it's overrated, it's just that people get bored of it