My own reasoning behind their placement
Sucrose: very good driver in taser teams, and a perfect unit to comp in any reaction based comps as she's able to swirl buff allies EM and VV shred, her grouping is also quite good and with cons she can further buff and become a decent battery.
Fishcl: the best electro character in game, delas off field damage with Oz, insanely good electro battery, insane electro application with no internal cooldown when she prokes her A4 passive, her C6 is very good but not needed as she's a good unit even at C0
Bennett: one of the best buffers in game, gives an insane attack buff, really good at healing, very good pyro battery.
Jean: has always been pretty good but thanks to Furina released her value has improved by a lot, can hold VV and has a teamwide healing which has great synergy with Furina.
Diluc: he found his new best team being with Xianyun as a plunge unit thanks to his high plunge multipliers and they are quite competitive
Klee: very solid pyro dps with lots of pyro application, can feel clunky to play but in mono pyro teams that shouldn't be too much of an issue. Great pyro battery and very good C2 which can buff the whole team's damage.
Venti: the best anemo grouper against enemies that aren't too heavy his value has diminished due to enemies being heavy but he's a good comfort pick when he can lift enemies up with a nice energy refund passive and buff due to being a VV holder.
Albedo: relatively good unit who's a good flex, can provide crystallised shields, EM buff and off field damage
Eula: Needs to be well invested to feel good to play, her damage can be very good and has good nukes potential.
Mona: good buffer which can enable nukes, best played in freeze teams to maximise her buff and can be used as the hydro driver in any dendro comps if needed.
Kaeya: good off field application and damage, versatile in team comps, good cryo battery scales well with constellation.
Rosaria: good at both buffing and dealing damage, crit rate buff is very nice. Good cryo battery her best cons are C2 and C4.
Noelle: A very good driver for Furina teams as she can consolidate the on field and healer role, has very good AOE.
Barbara: her value has definitely improved with recent releases, she can be a good hydro healer for Furina thanks to her teamwide heals and she's a good unit to run alongside Nilou bloom teams.
Lisa: good general electro dps, her best teams are in aggravate and with cons she can defence shred which is quite valuable.
Diona: can do a bit of everything, shields, heals and a good battery; with her C6 she can buff Em which are good in melt teams.
Razor: Isn't a good unit but is usable to trigger both burgeon and hyperbloom in dendro teams.
Mika: dedicated physical support who doesn't really synergise well with Eula to to buff uptime, found his niche with Furina by being a teamwide healer and can buff attack speed.
Anemo traveller: great F2P unit that can hold the VV set to shred enemies elemental resistance
Amber: her best use is holding the Elegy of the end and for minor pyro application with her burst