Why oh why didn't they go with elves? Or just fox people WITHOUT a snout and just the ears? If only...
The worst part about Warriors All Stars is that it is not bad. It is rather shockingly good, no matter how much you wish you could just skip it and move on to WO4. It is a musou developed by the Hyrule Warriors half of the musou team which makes this one the closest that team has gotten to mainline musou development. This is good, the Hyrule Warriors team is great at making a wide variety of movesets with more bombast than typical musou content and they insist on a dodge roll that can cancel out of charge attacks complete with some unique properties on summons/projectiles you dodge canceled out of firing. The dodge cancel alone improves the standard musou flow in ways so astounding that SW4 and DW9 both added something similar after being humiliated by it in HW and OPPW3. They're also great at simplifying standard musou equipment farming so that you aren't putting the same 6 overpowered seals on every single weapon forever because those are the only useful ones.
Plus since it is based off DW/SW, you don't get the awful bosses from Hyrule Warriors or the logia crap from OPPW or the weapon triangle of FEW or what have you. The gameplay is as pure as it can be.
But what that team is weak at still shows up here: The maps themselves are all great throwbacks to the various games, but the mission design in them... let me step back here and say the ENTIRE game is built around base capturing and raising your "Bravery" stat, which is essentially standard musou morale quantified. If your bravery is 3, the angry knife waifu with bravery 6 is probably someone you shouldn't fight right yet. This gameifies each level so you aren't usually wasting time waiting for scripted nonsense to happen, but it definitely makes every level feel like randomly generated crap. In fact, the entire world map of the game is dozens of randomly generated levels you can play freely with a few story levels you actually need to get to. No mission in this game is memorable, and they all rely on you capturing bases and doing sub-missions to raise your bravery so you can tackle the main objective. It is a very interesting idea, but it comes at the cost of anything approaching a memorable level.
In addition, there is no tag system. Well, there IS, but you will never want to use it. You equip 4 teammates along with your player character, but the 4 teammates give you active skills on cooldown that are almost all massive damage, massive buffs, or some other game changer. Rare for a musou, they're almost all really good and give you a nice variety of options. Unfortunately, the cooldowns on these skills stack with the game's anemic tag system, and you would almost NEVER want to tag instead of using a cooldown skill.
Gear is simplified down to a single equip: Cards. One card per hero. A card has an attack stat, an elemental slot, some friend buffs, and 1-4 slots into which seals can be fused. You can swap elementals by sacrificing another card or attach seals using mats but that's all you can change on a card. The game drops dozens upon dozens of cards on you and they are almost all useless and you are constantly selling a half dozen marginal cards per mission. Getting a card even WORTH spending loot to upgrade is a game-long endeavor; the gacha here is terrible and stacked with Fire-2 one slot cards, but thankfully alright cards can still get you through most of the content.
The game is built for replays. You don't have a free mode, but you do have over a dozen endings to find depending on if you chase the main story or go for a character specific ending. of which there are quite a few. Rio, Honoka, and Marie decide to become idols, or Lu Bu decides he'd rather do what Lu Bu always does, etc etc, so all the randomly generated feeling content makes more sense considering how much of it you have to traverse. It's a good thing there are a lot of characters from Koei franchises. Atelier, Nights of Azure, Nobunyaga (I can't believe the guys who have been writing the only interesting Nobunaga depiction for 20 years managed a completely different Nobunaga depiction who is also a cat but JUST as cool while being very distinct from the standard musou demon king.), Toukiden, Deception (Where is my PC port? WHERE IS IT?!), Nioh, and even Rio for pity's sake. The game is packed with interactions and in-jokes from the various franchises involved. There's a barrel in the lobby, for instance. Oka from Toukiden does the sword sheathe thing from Toukiden. William can do his ki cancels if you really want to have some DMC style wrist cramping during a musou. Every character is just a joy to play even if some of them have a lot of moves that are more fun than useful.
If I had a meaningful, actual complaint, it is that enemies all can trigger their own hero skills freely, which stops you and renders them invulnerable for several seconds until the animation finishes, which really kills the pacing. If the enemy is Oka, she has the Toukiden shield which makes her invulnerable for far longer than any musou AI ought to be. In addition a lot of the random maps offer "Rescue Teammates" objectives that are mathematically impossible to clear even if you are wildly overleveled, but these are just non-story random maps. These are a minor pain, but for a game relying on you replaying this for arcade fun. they really need arcade perfection or else this stuff gets amplified.
Warriors All Stars doesn't deserve the hate it received and really could have used an Ultimate/XL expansion (Yes I am an idiot who keeps falling for Koei's "release it once and sell the endgame as an expansion" marketing scheme) to smooth out the rough edges. Everything about it oozes with love and charm and it feels like one of the fullest featured musou products we have had in quite some time, combined with combat put together by the (Generally more talented) mascot musou team, and you really have a solid product here that a lot of people have unjustly written off. It won't replace WO, but because it is so different, WO cannot replace it either. Having a musou try something different and actually succeed is so rare that if you are a long term fan of the genre (Or an Atelier/Toukiden/Deception/Azure fan), Warriors All Stars deserves a shot from you.