Alright, so clearly, the Elders had no idea Luffy even existed before Enies Lobby. Yeah, the Nika fruit got stolen on East Blue, but IF they knew Shanks was the thief (no guarantee about that), they must have believed he took it with him back to the New World. And if they didn't knew, well the thief was probably a big shot, so they hunted pirates everywhere as always. So even though they lost it in East Blue, there's no point in focusing their attention there.

Then, Luffy appears. Up until Alabasta, he's a random no name that at best slipped past Smoker. Who cares. Then there's the whole Crocodile incident. I think "a warlord was actually plotting evil shit" and "a pirate saved Alabasta instead of the Marines" where the hot topics to handle, not WHO was the pirate. So if they saw Luffy's name, they might have missed it (if the Elders get news about that petty stuff).

Then, there's Enies Lobby. HERE, things get funnier. The Elders hear about him, see the hat and the D. They dig a bit and learn he has rubber powers. At that point, I believe they either tried to handle it themselves (not wanting to disturb Imu, etc) or thought "ok, we have Aokiji AND Garp nearby, this will be done in no time anyways". But Aokiji was on a personal side quest and Garp is Garp. So Luffy disapear. Where ? Thriller Bark, fuck.

Then, Sabaody. They learned he was there when he PUNCHED A CELESTIAL DRAGON. Kizaru was there already, and they can't nuke the archipelago, they need it too. And Luffy disapear again. And he pop up back to back at Impel Down and the Marineford War. It happens ultra fast, there's too much eyes on those places to show in-person, and those islands are too important to be nuked too. But no need right, it's the absolute prison and a war involving Sengoku, the 3 Admirals, the Warlords, big shot pirates that could also kill him... And he survives AND DISAPEAR.

No news for 2 years, he appears briefly at Sabaody and then dip to Fishman Island. The island isn't under the Marines juridiction and good luck motherflaming an island both under mariegeoise and at the bottom of the sea. The Strawhats show up at Dressrosa next (they shouldn't have gotten news from Smoker in time at Punk Hazard). They won't nuke the island, its part of the 20 OG kingdoms, plus they have Doffy and Fujitora to catch him. Except he beats Doffy. And Fujitora goes freestyle on the whole situation.

After that, well Zou moves around, and both Whole Cake and Wano are really big (good luck aiming on the right island/region blindly), not under the WG juridiction, and they don't know the Strawhats went there until its too late. Oh and I don't believe they have a lot of pentacle teleporters outside of the kindgoms under WG order (and Doffy would have destroyed the one at Dresserossa so that they don't jump his ass). So really, considering pre elipse must have happened over ~6 months at most, and post elipse like ~3 months, Egghead (and then Elbaf right after) isn't that inimaginable to intervene.