Part of RE's charm was that it made you think, the point of the game was to survive in places where paranoid madmen had been in control. The police chief, Brian Irons in RE2 was a perfect example of this, he rigged the whole police station with puzzles and cryptic keys that only he knew so he could keep his involvement with Umbrealla Inc. as well as keep people from finding their secret, yet enormous, lab buried beneath the city. The puzzles were a mix of observation and fetch quests but they encouraged the player to explore the area, call back to things they'd observed earlier on and provided an excuse to move around beyond killing zombies. The later games made little to no attempt at puzzles and on that rare occasion they appeared they were turgid and monotonous. Take the Kijuju temple sequence in RE5, the whole level is a damned maze where you have to move statues, walls and mirrors in the right order to progress, only to end up at one of the most frustrating boss fights in the world against Wesker where the way to win is to time him out before he decides to disappear. What an anticlimax.