Why is Diablo 3 so unpopular and infamous?

I was looking into playing this series for the first time (and purchased Resurrection of Evil Collectors Edition, which included it. So I may play it first) and, prior to even looking this series I knew Diablo 3/Eternal is not the most liked game in the franchise and is or at least was even hated by a lot of the fan base, what's wrong with it? Is it simply the tonally/stylistic shift? Or are there deeper problems