Hello. I'm one of those dumb a-holes who repeatedly spawns and detonates my car near a spawner.
Typically this is only worth one kill before I die, usually to my own vehicle.
In my opinion, the cooldown is unnecessary, but it really only stops me from doing the above tactic.
Then again, I usually run it with brick, and launch the car at whatever area I want to blow up. This was very fun but usually not very successful as the other team would catch on very quickly. Car spawners are not exactly plastered with cover as it's a place that an entire vehicle needs to exist at; and they remember my vehicle design, bait it, and dodge, then kill me.
I personally think 90 is far too high. Maybe 45 would be a better timer. If anything.
If it was a good tactic, then you would see more players doing it. Non-meta tactics don't need to be nerfed. You should really focus on the things that people abuse on the regular such as swapping from a low damage pistol (damage is not noticed) to a high damage sniper to "one shot" people without them being aware. That gets me more than any detonator ever has.
The only reason people are mad at this tactic is because they got tricked into following me to my car. Fool me once, shame on you; fool me twice, shame on me. Just remember what my vehicle looks like.
Oh and just a quick addition, ALIG and mobile spawner are both ridiculously effective. Far more than remote detonator ever could be. RD is just a meme. ALIG and MS are S-tier meta.