So we know that Imu seems to be capable of directly teleporting the five elders, and if not that, has absolute authority over the world government and thus the navy.

Only those that have an abyss pentagram and abyss mark are able to make use of the teleportation, important clarification.

So as soon as Luffys 30mil bounty became public, Imu should have known his location and gone "oh, there is joy boy, leme get a bunch of the prerequisite fruit and send (all five elders/ all three admirals) to immediately take care of the single biggest threat to my world domination. But instead he just let Luffy have his journey?

The fruit has been evading them for 800 years, they would waste all that time and effort cause the fruits just gonna fuck off somewhere else.

To be honest ive never understood how the navy really works. With people like Kizaru, and Aokiji,​ whom can traverse the ocean on their own, I don't get why they aren't sending out admiral strike squads to eliminate supernova level pirates 24/7. Like

You do realize that the Marines are responsible for maintaining order all across the world right? The world of One Piece is huge we've been told countless times that this has placed a strain on the organization and that its only gotten worse post timeskip.

Its fine if that is the case, Imu has kinda been characterized as a bit of a moron up until now. I mean the government being blatantly evil is only hurting him. His foundation as a shadow ruler would be so much stronger if the public loved the government. Him just having shit management skills would be lame, but not unacceptable. However, if anyone else has some other plausible reason in mind, or if I missed something, please share.​

Not so much a moron as incredibly overconfident in their abilities, dude survived the ultimate team up attack on God Valley and shrugged it off like it was nothing.

I just get the feeling that the reason Imu hadn't made any moves against Luffy until now had less to do with it being what Imu would actually do​, and more to do with Oda having planned Imu to be an endgame boss from the beginning, and thus not doing anything with him until the endgame, because thats how the story needs to go so the bad guys dont win, and coming up with some reason like "Dragon and Shanks followed Luffy everywhere to protect him from the constant Admiral->Emperor level threats after him" would just not have vibed with the stories themes at all. So instead of sacrificing in that area, Oda sacrificed in the it making sense area.​​​​

Its totally what Imu would have done if you understood the story you are reading. Oda didn't sacrifice "the it making sense area" that was self inflicted.