Warband was fun. The AI changes in VC make the game almost unplayable and RIDICULOUS, STUPID, GARBAGE! Example: Arena fighting. Spawn with 6 other guys. Literally ALL 6 charge me, group up together, ignore one another, gang up on the PC. ALL OF THEM. And they can all get off attacks quicker than I can release one that I've already started, and do 3x the damage I do. The same happens in tournaments and the field. VC is an utter garbage fire and needs massive fixing to be playable.
No, it just takes getting used to - although I agree with you that the arena in VC is kind of stupid.
At the start your stats will be weak AF, so your attacks will of course be much slower than pretty much everyone. Just keep training/fighting, and you'll improve quickly enough.
Personally I think the arena fights are a bit of a crazy cluster-fuck, but they don't actually gang up on you all the time - quite often they'll go for whoever happens to be closest. Although there are times when it does appear that two assholes are chasing you and ganging up on you, that is true...
Honestly when I started playing VC I pretty much rage quit arena fights. Eventually I went back to it, kept at it, and found that as character skills increase, the fights become easier. It's a good way to get used to the weapons, especially the spear - personally I find the sword way easier, but you tend to get the spear more often than not, and the fact that ranged weapons are allowed is a bit stupid (so get ready to dodge) - and it sucks when you don't even start with a damn shield!
I have never managed to be the "last one standing", despite the many hours I've put in - I'm admittedly not good enough, despite my massive stat gains - but I have won the "proper" tournaments, organised by nobles in the cities whenever there's a feast there. These can be tricky too, and RNG can screw you up big-time before the fight starts due to which "team" you're on, but they're a lot easier to win in general since when you have team mates (which you will until the players get whittled down in later rounds), you can order them around. There are still 4 vs 4 battles (with multiple dudes per team), and your weaponry is still randomly assigned, but it's more manageable.
While I recommend playing the arena to get your stats up, it's not mandatory - you can just start recruiting dudes and taking small missions. These are actually WAY easier than the arena (initially), since you can just send your troops to do the fighting for you if you want. The AI changes for the non-arena fights are IMO much better - even if "shield wall" tends to be the formation for everything that's not archers or cavalry, and even if the AI can (usually) be exploited fairly easily...
If that still doesn't work for you, there are mods for VC. Not as many as "base" warband, but still. I'd recommend getting the "VC Balance Mod" from Nexus, as that fixes many issues with VC (not the arena as far as I'm aware, but other stuff).