Battlefield 1 historically has a bit of a grenade issue, and DICE is attempting to fix it. The They Shall Not Pass DLC came with a bit of extra balance changes in addition to its new content. The primary rebalancing focus is on grenades, particularly with how restocking works in tandem with the Support class.
Before, grenades came in a preset allocation. Because of that, situations like chokepoints became a battle of the hand-tossed ordinance, as grenades are powerful tools when tossed at groups of players. Dying and respawning was a quick way to restock, making defensive strategies all about blitzing, then dying to get the explosives back. Support classes seemed less useful, and this one strategy was being overused.
With Ammo 2.0, the name given to these adjustments by DICE, grenades now have a cooldown timer. Support players can now affect this cooldown, effectively making them more relevant to chokepoint-type situations, on top of overall limiting the sheer number of grenades overall.
DICE claims so far it has measured a 7% decrease in thrown grenades and grenade kills. Many fans appear to be upset by this change. However, balance changes are often needed to keep competitive games populated and long-lasting, so addressing any lasting problem is far more important than keeping things familiar.