You are incorrect.The designers made 5e, from the ground up, able to handle a no-magic setting.
The DM controls magic items.
In a setting where magic items are scarce, the DM can − legally − remove magic items from plugged-in official adventure.
Also, a DM can swap magic items around, and add extra magic items.
5e is built to handle DM discretion.
The designers made 5e, from the ground up, able to handle a no-magic setting with little modifications.
That modifications are:
- Allowing warriors to silver their weapons by a certain level
- Severely limiting the usage of very supernatural monsters
If you run a no magic setting, that goes for the monsters and enemies too.
The base game of 5th edition is magical though. If you run that, the game assumes ~1 magic item per 4 levels and a bonus magic item at 14 and 18 as the bare minimum of play per PC. Plus oodles of potions.