This is another reason why the old loose cluster marshal armies from Warband were so much better than these Bannerlord armies. The warband armies actually could chase after small parties, but that's because it wasn't the entire army but a couple small, fast lord parties that could break away from the pack to chase down passing enemies. The loose armies did a much better job of replicating how a big armies would actually march, which in medieval times could be more like herding cats than leading a crack force of disciplined professionals. It made those big armies much more dangerous because if you got too close, some weak junior lord with 30 troops could rush out from the crowd and actually catch you. Warband let you get into towns under siege with no penalty, but to do so you had to get past 20 separate parties camped outside. But you also had a lot more tactical options when facing those marshal stacks since there were ways to break them up and isolate stragglers. Bannerlord armies are all or nothing. Attack them head-on or lurk behind waiting for the army to dissolve.
Leading those loose armies was also more interesting. You couldn't just bring 800 guys against 2000 enemies without most of them noping right on out of there, so keeping everybody together was half the game.