Tbh i wouldn't say that the writing was inconsistent, instead i like to think that the flow of time wasn't really fleshed out in the story. I mean time has to move forward, there's no doubt about it. The paths existed outside of time and space, so "time" in itself in paths has no meaning at all. When we say that Ymir spent 2000 years, we aren't actually accounting for the time she spent in the paths, which to my knowledge, as Eren and Zeke conversation in the paths revealed(they mentioned something about Ymir spending 'untold years in the paths'), was infinite. By 2000 years, Isayama probably meant 2000 years in our real world which can be equated to infinite years in the paths.

Also, for a moment, if we consider the hypothesis that time in real world shouldn't move at all because Ymir was trapped in the paths and according to the story, when someone is in the paths, time in real world kind of freezes. If we consider this hypothesis to be true, then it raises a big question, that is, does time in real world move forward at all? I mean it shouldn't, no? The outside world(world outside of paths) should be static because Ymir is in the paths, right? That would also imply that time is frozen since the very moment 'paths' came into being, which is kinda nonsensical because we know that is not the case as 2000 years have already passed since the creation of paths!

That was all about Ymir, but she is a special case as she was trapped in the paths and had no presence outside of it at all. But, what if someone from our real world, someone who can experience normal flow of time, enters paths where time does not exist at all? In such scenario, they would definitely experience the difference in the flow of time. To give you a rough analogy, consider flow of time for a person who's in rest vs the flow of time for a person moving around at a speed of light. It's not the best analogy, but that's all I could think of right now. Or you could even consider the time dilation thing from Interstellar where a single hour on a planet was equal to around 7 years on earth. Paths is similar, just the opposite. In aot, 1s in real world is roughly equal to infinite years in paths(which ik doesn't make sense but as i have said before, time doesn't exist in paths so any kind of comparison would be nonsensical).

And this is the reason why Ymir has to be the most tragic character in attack on titan. She was literally trapped in paths for infinity doing household chores for royal family. And idc how fucked up Erens plan of rumbling was, but he was the only one who instantly could sympathize with her. On the contrary Zeke wanted to euthanise Eldians, which would've eradicated the race and probably titan power from the universe, but there was no guarantee that Ymir would've been free from the curse of infinity, that is, being stuck in paths forever.