Your map is surrounded by a ring, which will slowly close as time progresses. This reduces the field of play. Try and stay inside the ring – stepping outside will cause damage.
Since their somewhat outdated engine wouldn't allow for the graphical fidelity seen in other state-of the-art games, Respawn was hesitant to use it for the creation of Titanfall 3. Instead, they came up with Apex Legends as a last triumph before moving on to a new engine.