Limit the Titans
This sounds like a very weird request, admittedly. The whole point of Titanfall is that you can summon a giant robot to turn the tide of battle, yes. After all, they feature pretty heavily in the marketing, and the game is literally named after them. But hear us out.
There’s nothing wrong with a shooter that just wants to offer the player endless action for 4-10 hours (see: the new Doom), admittedly. And having giant robots at your disposal all the time is pretty cool, but if the whole campaign is just “on foot, on foot, parkour, robots-robots-robots”, the feeling of power you get when you summon a Titan could diminish if you’re doing it every five minutes.
Perhaps missions where you can’t use a Titan at all would help mix things up and not feel like one long haze of destruction. Say, the enemy will hack your Titan to fight for their side if you try to summon it, for example. One thing that would help is if the campaign missions limited the Titans you can use depending on the level or the objective. Or if a mission requires you to provide heavy fire or defend your faction from an incoming assault, the Ogre or Atlas would be the only two available to choose from while the Strider sits this mission out, for example.