The original doesn't need to be replaced, but the remake should hit the significant beats of the source material even if it's changed or added to in some way. Even though the failure of the A/B scenario implementation in RE2 is a big mark against it, I still think it's a great remake because it feels like a brand new game while, in some form, including almost all of the memorable things from the original RE2. Not everything, mind you, like some of the more minor areas, which is a shame, but it still does an admirable job in my opinion.
But RE3 remake apparently cutting several major areas from its source material is pretty staggering. Almost of all of the game's second half has been completely replaced. These new areas probably still would have been great to see in this remake, but in my opinion, not at the expense of the memorable and inspired environments from the original RE3. Plus, of the four major locales you explore after the rail car/subway train, they for some reason opted to keep the one that feels the MOST disposable and least distinct (the hospital) while axing and replacing everything else.