ARIMA is very very slow and computational expensive.

>Even if true, they could take a random subset of size 100 out of the 300k and compare on those.

Sure...but there's a chance that ARIMA won't even finish training on that subset either.

It doesn’t matter.

If you write a paper and exclude comparisons to state of the art, this what happens.

They could have done something, and didn’t.

“It’s hard so we didn’t” isn’t an excuse, it’s just a lack of rigor.