I can't tell if these are gripes with Bannerlord or medieval warfare.
I agree with some points, but others depend on other features and player savvy. IE the only times I lose troops to sea bandits is if it's a 20-stack and I want to train up recruits super fast so I just fling them at them with minimal support.
If you time archers volley right, they'll raise their shields and lose 1 volley of javelins. They're also super prone to Idiot-magnets, so alone or with heavy cav you can make half of them waste second volley and have your infantry close to melee.
Then there's the matter of purpose. I clear high stacks to get low stacks that then can be recruited and put into your castles, as well as to weaken their lairs, to wipe them when they're on 1-2 groups inside.That's actively reinforced by game mechanics.
#6 - Everyone is in reality running dragoon armies like this. There will come a point when you have to make the call - have fast cav, or be able to up-train troops. A middle ground if having specifically dragoon units (infantry that matches cav speed if saddle horses are provided), but in general this is an issue warfare centred around still in WWII (the infamous pictures of Polish cavalry charging German tanks - the cav units were used for transporting anti armour guns between ambush positions), and most ages before (Mieszko I is thought to have conquered early Polish tribes with ~100 very mobile mounted soldiers, talk about an exploit!).
At least with perks not working, crossbows are still weak. Vatican (Urban II in 1096 andf Innocent II in 1139) had to issue a patch in real life to combat that power creep.
As for companions - I'm currently scouting the map for companions with tactics skill - they're rare and expensive (2k+) which can make us prone to getting the crappy ones if we want someone fast, but require taking your time if you want an actual commander. Having had very little luck finding ones with tactics I somewhat symphatize, but this again is dependant on player execution, the pieces are already there.