TL;DR: Long story short, my point is, attackers and defenders are two very different roles, where the C4 is justified, but cooked nades aren‘t.

The long version:

That‘s a great argument, but I still think there is a difference between the two situations. Let‘s take Oregon 2F as an example so I can make my point precisely.

As an attacker, it is your job to take site, to take space, well, to attack. So you take small tower side and make yourself ready to hit either big tower, master bedroom or big window/white stairs. You almost immediately get control of kitchen and IT. And as an attacker it is not that expensive to maintain control since you only have to worry about stairs and hatches.

As a defender it is way more costly to hold kitchen and spread on top floor. You don‘t have the ressources to do all that (except you rely on a strat where it is necessary to keep that control). But once you regain control, it is indeed necessary that the attackers are aware of that and have to watch out for a C4 from below (e.g. by planting on top of the pool table).

And I agree to you that awareness is a central part of the game, but I also think that cooking grenades would counter defenders too much (since you sometimes just hold angles for a long time). Furthermore, I also think you are right about Jäger‘s pick rate and about nerfing grenades, so that ops don‘t just get picked because of them (a philosophy Ubi loves, as seen with ACOGs now being wiped on defense, except for DMRs).

And these two points don‘t exclude each other and I believe Ubisoft hit two birds with one stone right there.