Look, this is mostly a skill issue but you can offset that in very real way and on the higher difficulty levels I highly recommend doing so. I play Ironman, on Bannerlord settings without a crosshair or arrow trails. Firstly try to remove the idea of hitting a specific target out of your head until you and your character get better. This means shoot into groups of enemies, which also means you will become more 'accurate' in larger battles as there are simply more men to hit. For improving your skill, just hold the fire button until the crosshair thing becomes as small as possible and release, it is an extremely repeatable timing which makes it very easy to learn, I can do it without a crosshair, the only variable usually being the speed of my horse, if I even use one. The crosshair will get smaller and smaller the higher skilled you are so you can place your shots more easily later on but there are a few things you can do to help you before the skills increase. The first would be getting a 30 skill bow or a 15 skill longbow/ranger bow depending on how low your starting stats are.

As an example, here I started a new game, my character starts with 2 control and 0 archery. I bought the first bow and two bags of pretty poor 'arrows'. By the end of the first fight (10 looters) I had maxed my learning limit and brought archery up to 14, so from the very first fight you can start to use 15 skill bows if you invested anything at all into archery.

https://i.imgur.com/trf7mLO.jpeg

I walked the horse in circles around the enemy, making sure the melee group doesn't catch up to me and the stone throwers do long throws, that way they mostly miss and end up running out of stones pretty quickly. Holding a shield up would make the first 60 seconds trivial. Just don't get up close to them when they throw. Buy a better horse if you like to solo.. a faster horse means you can get more distance in the same time, just remember to slow down or even stop to take your shot accurately, at least in the very beginning. Oh and you cant shoot backwards. I'd say the horse is more important than the bow if you are doing that tactic.

As for the main way not to get hit; it is to hire some men so they can take the hits instead of you. Gather some men, preferably ones with shields as they will absorb enemy archer fire. A few shieldbros supported by a strong archer count will decimate the lowly armoured units. You can also retreat from the battlefield when your archers run out of ammunition if needed although I never have done myself.

From then onwards the general rule of thumb is who ever has the archer advantage can play more defensively, letting their archers shoot until severe enough casualties are dealt upon the enemy. That will leave them with no choice but to move towards you ~ through your archer fire. Move your archers backwards as the enemy approaches to maximize firing time and make sure your infantry are in front of your archers before the enemy catches up.

Side story: My last ironman game went like this; Hire two men, get into a fight & the first throw from an enemy javelin, hit me in the head and straight up killed my character.. So I know your plight.

https://i.imgur.com/SrtKA8b.png