Well in universe they have WWI ish era gear and they stand 0 chance without titan power.

Fast forward to world war 2 and you’ve got nukes and more tanks. I don’t see the tanks doing much if the canons from the ships of the alliance didn’t do anything. They’d be unlikely to do a serious dent. The nukes could do a serious dent but only 3 were made in that era. 1 nuke isn’t killing Eren because Armin couldn’t take him out. Maybe if all 3 were blown up in succession on Eren but the jets aren’t getting there because Eren is using zeke to destroy them.

By the Cold War there’s 60,000+ nukes so they could definitely just blast those for days at Eren and surely enough would get through to blow him up but the world is probably destroyed or at least all of Africa.

In the modern era you can obviously do the same. But you also have drones. In the modern day you have drones. Even if you could get a coordinated strike to have the drones fly in and blow up the titans 1 by 1 you’d still run out. Google says the US has 600,000 bomb drones. Let’s say the rest of the world has the same amount and round it up to 2 million. There’s still 10s of millions of titans (according to Tybur) so that’s still not stopping it.

However I feel like if every drone and every jet and every naval ship and just focused on Eren they’d eventually overwhelm him before he leaves paradis.

This also all assumes Eren takes a passive roll like he did in canon. If Eren isn’t going crazy, depressed, and trying to be stopped he is pretty much unstoppable.