5. How can we change that?
All in all, it's pretty "simple". Adding some pressure would help.
First, I would like to say, any changes of the sort should either come very gradually, or be restricted to the highest difficulty/difficulties, such as nightmare.
As for the solutions...
-Ammo/Health limitations :
Unfortunately, can't really change that without removing power from the player, since both of these are made infinite by builds, not by default.
-Limited revives :
It would work, but not on it's own.
It may be interesting to consider giving back revives to the players by accomplishing objectives, so as to not punish doing extra things too much.
-Spawning/Respawning Enemies/Traps/Structures :
An interesting thought as a whole, there are many many ways to balance this.
For example :
-Spawning and Respawning enemies could be ethereal/ghosts, like the ones coming from spawners
-Traps and structures could have a distinct sound to warn the player, and structures specifically could even have a way to prevent them from spawning if taken on early enough
-More aggressive storm triggers
Patrols of enemies going around the map, elites that can trigger storms, traps that may be harder to avoid... There's quite a few ways to handle this.
-Timed storms
In the same way DRG triggers swarms at regular intervals, triggering storms automatically can be a solid way to threaten the player.
-Storm enemies do not drop anything
This speaks for itself, there's more than enough ways to get more powerful as is, triggering a negative event on purpose to grind more rewards is very backwards, and removes the punishing part of a punishment.
-Enemy ramp up
Technically many ways to do so, but I believe the best way to integrate this would be that every storm is worse than the last. Mainly through spawn budgets, or having more elite enemies appear.
Additionally, it may be interesting to have a sort of ramp up during infinite storms, such as the objective, boss, or extraction, to avoid the player progressing through these at a snail's pace.
-Hard timers
A risky method if implemented badly, however, there might be nice ways to implement this :
-Extraction timer, a timer that would trigger AFTER the boss has been killed, forcing the player to escape in a limited amount of time. Would pair especially well with an extraction that requires the players do actively do something other than just survive
-"Cataclysm" style timer, a timer that would trigger a very negative event, such as :
-Mission start timer, triggers infinite storm when at 0
-Mission start time, triggers a limited, but very dangerous event, resets the timer after it triggered
-Boss start timer, triggers a boss "enrage"
Time based threats :
A lot of games do something like this, by having an oftenn unkillable (or nearly) threat that appears after too long of a time has passed since the start, or since the last time the player did something to progress.
-# It can also double as a nice "secret" objective, if you make the threat nearly unkillable
-# Underlined are the ones I believe to be the most effective, and I suggest
Now... These don't all have to be added, of course. In fact, some should be mutually exclusive.
But the game should, at the very least have some forms of pressure.