You rely too much on Macdonald and he was not an engineer and he missed the work that had to be done on the Berezina as well as being defeated regarding two rivers-the Tribbia and the Katzbach.
The crossing of the Elster was by a causeway a mile and a half long with several bridges along the way. And that was also over a swamp. And even a 'small' river that is steep-banked can be impassable for artillery and trains.
If for nothing else, Dulauloy proved himself unreliable by not taking personal charge of the bridge and the demolition and leaving an engineer colonel in charge who subsequently deserted his post.
I would recommend getting a good map of Leipzig, specifically the area between Leipzig and Lindenau.