There's actually a lot of new features, they are just integrated to main mechanics to create a more free form puzzle box level design.
In Blood Money, there's mainly three ways to pass blocked paths: disguise, alternative paths like water pipes, and keycard. The latter is often reserved for highly important areas, and securing a key is, depended on your aim, a secondary objective. A prime example of this is A House of Cards, no elevator card = literally can't progress (unless you go with sniper). Curtains Down in some capacity is the same with the light control room.
WoA tried to fix this with varied items with different functions. So now in most the maps, you don't really need to find a keycard but a lockpick or a crowbar can do the trick with a door, a shaft requires screwdriver, a machinery requires wrench. If there's a path that requires specific tool, then the game makes sure there's one more source to get them. For example, in Chongqing you can find various floor access dongles for the same floor, but there's only one dongle for a different floor (in level 2, you can find a lot of level 2 dongles, but there's only one level 3 dongle in the security room, because realistically only Royce and the guards can move between these floors). If you go with suit only or can't secure level 3 dongle, you have the shafts.
Basically, play a level at least twice and you can see the design of WoA is far more different than Blood Money. It encourages memorizing item placements and pathways, with item diversity helping improvising choices, and items have more purpose than just to throw. This also explains why you can't carry more than 3 items. You have access to alternative entrances that shorten the paths to get necessary tools, so it's your turn to make use of map knowledge to get them. If you can just start with a switz knife that can open every path then the map is no longer worth discovering, they are forgiving enough with permanent opened shortcuts anyway.
The maps are filled with accidental kill opportunity, but often targets are accompanied by a guard so you can't just wait for them to walk into the trap. Some traps like electrified water not just requires specific tool but also timing, because in some case if you sabotage the plug too early, it can distract another NPC nearly early and kill them instead. It finally dawned on me in season 2 that IO fixed a usually unnoticed flaw in BM: targets walk into a room alone way often. In Hitman 3, there's a lot of work if you can make that happen. I've played most of the assassination attempts in Dartmoor and the only one where Alexa is alone is the graveyard one, and even then you have to hit her right when the guard turns away. In Chongqing there's only two ways to keep Royce alone, one in the core room where you have to fire a guard and the operational staff (or block the glasses in her room), and the other way which involves too much choking staffs, and again blocking glasses, if you go with accident kill then you must have poison or a screwdriver, so on.
very poor arsenal with plenty of mark 2 and 3 items, not being able to carry more items from the beginning but you can carry everything you find in a level, not being able to modify weapons, no blood trails, no elevators and no elevator hiding and strangling, no sniper rifle assembly and disassembly animation, no newspapers, no human shields, no notoriety and blood money system, no looking through key holes, no showing what direction NPCs are facing when looking at the map or minimap, no NPC disarming, no dual wielding. Whatever, order of mention is not necessarily order of importance.
BM also had its faults, but that doesn't justify removing features instead of fixing or polishing them.
Honestly out of these I can only agree with elevator, since it can spice up traversal in maps that have more than 1 building. IMO modifying weapon is unnecessary in a game where you don't use weapons that much aside from a silenced pistol and sniper. Blood trail is debatable but the way the game encourages you to knock people out non-lethally, they probably just thought it would complicate NPC's behaviour more than necessary. Sniper animation is... well it's cool I guess. Newspaper, not necessary since the targets you go after are purely personal. Notoriety, yeah it's a cool feature but I don't think it fits with the personal storyline and theme in this game. Looking through key holes, not necessary since you have a real time minimap. No showing NPC direction, not necessary since the real time map exists and giving the cones just makes it easier to avoid them. NPC disarming and dual wielding, I honestly don't think they're that important, to be honest.
It's just that more doesn't mean better. WoA games are way more complex and less dimensional in mechanics, while feeling more forgiving and free form than BM. Even with the breadcumbs (which you can turn off, and often you can just follow what they talked about).
In WoA you also have those challenges that tell you all the ways you can eliminate a target. What happened with you discovering that stuff on your own?
There's a lot of assassination challenges that are redacted. It's the usual AAA checklist design, but I personally don't really glance at them unless I'm really bored, and it's totally possible to find them out organically.
TL;DR: they're really different, even if on paper WoA doesn't have more mechanics than BM.
