[fgfarben]

A heavy battery makes an ebike extremely unpleasant to pedal manually. You should try it.

I built almost exactly the same size pack (2 kWH) as Jacques in 2020 on a hybrid road bike and hated it so much that I only rode it 20 times or so. The battery still sits in the corner of my house doing nothing.

[Panzer04]

It goes without saying that you need the electrical components to be operational and assisting, otherwise yes you are just hauling around weight for the sake of it. As the other commenter mentions though, on flat terrain this doesn't matter much (since wind resistance tends to make up most of the friction at speed, and is independent of weight)

[lukan]

On a flat road I disagree, but uphill you notice it a lot of course, but way worse is carrying the heavy bike. I take mine into trains a lot and unfortunately there are often lots of stairs and no escalators involved.