Drew McCoy has provided a stream of information about Apex Legends recently, and one interesting bit is why it doesn't feature titans, despite being in Titanfall universe. That's because they would be either imbalanced or not satisfying.
Respawn Entertainment initially kicked off the development of Apex Legends based on Titanfall 2 so, naturally, it involved the giant destructives machines, but they were later dropped out of development. Drew McCoy explained the reasoning behind this in an interview ith Game Informer.
McCoy went in-depth regarding Apex Legends' early days of development, explaining that titans are not the only game mechanic that got cut. He mentioned wall running and double jumping as examples of mechanics that felt incomprehensible, which made them "not strategic or learnable".
In essence, Respawn Entertainment focused on lowering the entry barriers as McCoy gave an example of a player performing those feats as having fun while doing so, but the players who get killed by an unseen enemy "who's going a thousand miles a minute" would have far less fun. He described this as one of those moments that are not learnable and the fact that it was someone else affecting the player who had no control over it was simply not fun and it got cut.
Titans themselves shared a slightly similar fate to wall running and double jumps. Introducing them to Apex Legends at the same power level they had in Titanfall and Titanfall 2 would be "incredibly unbalancing" because titans would just squish pilots around.
If brought to a balanced state, they would feel like they were made of paper or wouldn't have much power, which in turn would not be fun as titans always felt like a power fantasy. If it becomes a balanced tool, then it's not much of a power fantasy, is it?
It appears that Respawn Entertainment succeeded in creating a titan-free environment that is still fun though, as many other Titanfall mechanics were implemented, although not everyone can have access to them at any time. Pathfinder has a grappling hook and no one else does, but teleporting players around with Wraith or baiting enemy teams with them opens up many new interactions and adds layers of depth for this unique battle royale.