>Essentially you "own" the rented appartment.

Possession vs Ownership. In some countries, there law makes a difference and in some like Switzerland and Germany, for example, the possession of an object (or apartment) gives you a number of rights that the landlord can't annihilate by adding more words to a contract.

While in germany the landlord is the owner of the appartment, they have no right to enter it as they want, use it as they want or do anything but emergency work without the permission of whoever pays rent.

On the other hand, since the renter is not in ownership but mere possession of the apartment, they can´t do as they want either; they can't take down a wall even if it's cleared by an engineer to be safe, the landlord has to approve any permanent changes to their ownership unless the contract gives the renter some free reign.