You can get decent troops if you run an army with a few of your companions leading parties. When you visit villages they snatch up all kinds of troops, even nobles, that you cant, and then you can transfer them to yourself.
I personally find capturing bandits and training them into nobles to be quite fun, but that's the only aspect I think is somewhat fun.
Overall though I agree, it's not fun, badly designed, and it was better done in warband, mainly because it had the trainer skill and global battle xp gain. In wb, when you get to high level, and if you invest into intelligence -> training, it makes a big difference, and if you level up training in your intelligence focused companions, then you can really level up a band of fresh recruits into top units pretty fast, and it feels rewarding - you grinded your levels, and invested into int, and now you don't have to worry about your army all that much.
This was expanded in mods, some of which add very high lvl troops that take time to level up even with high trainer and lots of fighting, but it feels cool.
What you have in this game, is the perk in leadership, that adds a bit of xp, and that's it. It's impossible to level that up in companions as far as I know, so that's all you get. And then you get the disciplinarian perk to level bandits, but thats it. There is no investment you can make into troop training, or anything, just those 2 perks you get early on.
This ends up with a situation where you have to keep your troops alive in lategame, just like you did in earlygame, because losing them just means hours of grinding.
This is certainly a design mistake, as usual here. The main problem, I think, is this new skill system. The solution would be to have stewardship (for example) give like +0.1xp per skill level to troops below your level, and/or a mid/late game perk, that works something like - "every level gives troops below your level +0.1 daily xp", or - "every level above 200 gives +1 daily xp to troops below your level". That way, you will have to invest focus and stats into stewardship (as an example) if you want to train your armies faster. Stewardship can also be leveled by your companions if they run parties, so that way you can train them and, if you want, move them back into your party for some even more boosted xp.
This would be akin to how training worked in warband - investing into intelligence and training was costly. You could instead just get agi/str up and become an xp farming killing machine faster, but you have to choose between army xp and yourself, so it was a meaningful choice, and it all required grinding, for which you get rewarded
The solution I described above for bannerlord would be based on similar design principle - invest focus points etc into a skill that trains troops faster, so lategame you don't have to worry about training fresh troops and can screw around more and stuff.
Although I'm not sure if there is global battle xp - in warband, if you level up your fighting skills, you can kill a lot of stuff yourself, so the troops quickly get the global xp and that speeds up too. But that's again a problem with the new leveling system.
The economy is something they are already working hard on.
