For the bolded part.
We should a bit more precise.
The game as written does a good job.
But the writings do a poor job in conveying the intent and the RAI.
It is not evident, if you do not carefully read the DMG that the game is based on the assumption that there should be 6-8 encounters between long rests.
It is clear that there is an exp budget for characters and that this budget is to be adjusted for the number of players.
What is less clear is how to divide the daily budget into a meaningful adventuring day that will not be too easy or too hard.
In using "natural" language, the game became easier to handle and learn for the neophytes. But it also blurred a few rules and made them relatively hard to handle once you get stuck with trickier situations.
Ironically, 4e was the exact opposite. It's mechnics was designed blatantly and openly to run a multiple encounter adventuring day with various numbers of players and enemies. However it was so unnatural, different,and sometimes ugly that it turned off many from even trying it.