Sample teams (always accepting submissions)
:amoonguss::pelipper::gyarados::magnezone::kingdra::zapdos: Rain
:cloyster::togekiss::garchomp::krookodile::zamazenta-crowned::regieleki: Dual screen HO
:garchomp::hippowdon::dracozolt::porygon2::corviknight::dragapult: Rach's sand
:melmetal::slowking-galar::hippowdon::garchomp::corviknight::conkeldurr: Rach's balance
:pheromosa::slowking::magnezone::hippowdon::rillaboom::corviknight: Rach's phero+SD rilla offense
:clefable::toxapex::landorus-therian::rillaboom::pheromosa::slowking: Ivy's balance
:hippowdon::clefable::toxapex::corviknight::dragapult::magnezone: s1mpp's semi-stall
Viability ranking
A+
:Clefable:Clefable
:Conkeldurr:Conkeldurr
:Dracozolt:Dracozolt
:Reuniclus:Reuniclus
A
:Corviknight:Corviknight
:Dragapult:Dragapult
:Hippowdon:Hippowdon
:Magnezone:Magnezone
:Salamence:Salamence
B+
:Azumarill:Azumarill
:Garchomp:Garchomp
:Gyarados:Gyarados
:Hawlucha:Hawlucha
:Kommo-o:Kommo-o
:Krookodile:Krookodile
:Marowak-Alola: Marowak-Alola
:Ninetales-Alola:Ninetales-Alola
:Rillaboom:Rillaboom
:Slowbro:Slowbro
:Weezing-Galar:Weezing-Galar
B
:Blissey:Blissey
:Dragonite:Dragonite
:Ferrothorn:Ferrothorn
:Gigalith:Gigalith
:Heatran:Heatran
:Kartana:Kartana
:Landorus-Therian:Landorus-Therian
:Mamoswine:Mamoswine
:Porygon2:Porygon2
:Slowbro-Galar:Slowbro-Galar
:Thundurus-Therian:Thundurus-Therian
:Toxapex:Toxapex
:Tyranitar:Tyranitar
:Weavile:Weavile
:Zapdos:Zapdos
:Zeraora:Zeraora
C
Certain use cases can make these relevant with proper team composition.
:Alakazam:Alakazam
:Amoonguss:Amoonguss
:Barraskewda:Barraskewda
:Bisharp:Bisharp
:Blacephalon:Blacephalon
:Bronzong:Bronzong
:Chandelure:Chandelure
:Cinccino:Cinccino
:Cloyster:Cloyster
:Crawdaunt:Crawdaunt
:Diggersby:Diggersby
:Gastrodon:Gastrodon
:Gengar:Gengar
:Goodra:Goodra
:Hatterene:Hatterene
:Heracross:Heracross
:Hydreigon:Hydreigon
:Incineroar:Incineroar
:Indeedee:Indeedee
:Kingdra:Kindra
:Melmetal:Melmetal
:Mew:Mew
:Milotic:Milotic
:Mimikyu:Mimikyu
:Nidoking:Nidoking
:Pangoro:Pangoro
:Pelipper:Pelipper
:Polteageist:Polteageist
:Regieleki:Regieleki
:Rotom-Wash:Rotom-Wash
:Sandaconda:Sandaconda
:Sandslash-Alola:Sandslash-Alola
:Scizor:Scizor
:Sigilyph:Sigilyph
:Skarmory:Skarmory
:Slowking:Slowking
:Slowking-Galar:Slowking-Galar
:Stoutland:Stoutland
:Tapu Lele:Tapu Lele
:Togekiss:Togekiss
:Tyrantrum:Tyrantrum
:Venusaur:Venusaur
:Xatu:Xatu
:Zamazenta-Crowned:Zamazenta-Crowned
D
These see some use but are more often than not a burden. Not recommended.
:Accelgor:Accelgor
:Aggron:Aggron
:Araquanid:Araquanid
:Arctovish:Arctovish
:Barbaracle:Barbaracle
:Braviary:Braviary
:Butterfree:Butterfree
:Cradily:Cradily
:Druddigon:Druddigon
:Eldegoss:Eldegoss
:Galvantula:Galvantula
:Golurk:Golurk
:Hitmontop:Hitmontop
:Inteleon:Inteleon
:Linoone:Linoone
:Machamp:Machamp
:Ninetales:Ninetales
:Perrserker:Perrserker
:Relicanth:Relicanth
:Sceptile:Sceptile
:Scolipede:Scolipede
:Shuckle:Shuckle
:Swoobat:Swoobat
:Torkoal:Torkoal
:Vanilluxe:Vanilluxe
:Zoroark:Zoroark
Absolutely ecstatic to finally see an official viability ranking. Here are my thoughts on some of the pokemon.
Clefable- Easily one of the best pokemon in the metagame, shuts down stall without Geezing along with often shutting down HO because it leaves it with their setup pokemon obsolete, leaving only cleaners and revenge killers.
Conkeldurr- Anyone who's seen my posts on here knows what I think of Conk. With Mosa gone, easily the best pokemon in the metagame, and, in my opinion, too restricting in teambuilding and battling.
Dracozolt- The only thing keeping this mon from being banned is its reliability on weather. So little can actually reliably counter it under sand that it's ridiculous.
Corviknight- Now doesn't even face competition from Skarm in the role of a defensive steel/flying type due to Skarm having Weak Armor. Skarm still does have Toxic, Roar, and hazards, but with Weak Armor, it can't hold a candle to Corviknight.
Pult- Just overall reliable as always, even moreso due to opponents being unable to lower its stats as it doesn't have to choose between Infiltrator and Clear Body anymore along with being able to be an annoyance with Cursed Body.
Mag- Can potentially be absolutely insane, but has trouble reaching said potential due to being the only "real counter" to Zolt and being forced to run Tri-Attack for it along with the loss of Hidden Power in the transition to generation 8.
Azu- Two 4x resists to some of the best attacking types in the game along with two immunities, one to another extremely offensively potent type, the other turning a weakness on its head, and it gets to keep Huge Power? Wild.
Intimoxie mons- Extremely reliable combination of abillities, especially considering 3 get Dragon Dance. Surprised not to see Scrafty mentioned at all on the list. Debatably as good as the others due to status not being a complete counter to it with Shed Skin.
Kommo-o- Keeps Soundproof while getting immunities to many more moves and not taking hail or sandstorm damage. Maybe not the most impressive on paper, but quite good in practice.
Hawlucha- Not too reliant on terrain anymore and can be scary if used properly, but also often struggles.
Alolawak- Free extra immunity without Flare Blitz recoil and ok bulk with Cursed Body annoyance makes this surprisingly amazing.
Slowtwins (not Galar)- Not being able to be Taunted is wild for these mons as it lets them pull off everything they normally do without needing to give up Regenerator
Geezing- Amazing, but often pretty overrated. Glad to see it below A tier. Let me explain: while Geezing is an amazing physical wall that can handle many of the metagame's top offensive threats, that's the problem. It's tasked with handling many threats without any form of reliable recovery, only having Pain Split, Rest, and Protect+Black Sludge. Geezing can also be hit by status despite its own terrain because of Levitate. Without reliable recovery, even despite its Spikes and Toxic Spikes immunity due to Levitate, Geezing gets worn down extremely easily by chip and passive damage, especially if hit with a Knock Off.
Pory2- With PoryZ being banned, I expected Pory2 to be the next big thing. It turned out to be great, but not as overbearing as PZ. Sadly, it has to hold Eviolite, diminishing much of its potential power, but it's also extraordinarily bulky and hits surprisingly hard thanks to Analytic and Download possibly boosting its special attack.
Glowbro- Surprisingly good despite what, on paper, seem like rather meager defensive states. 30% chance to move first each turn and turn the tables on a threat is extremely helpful in tandem with its massive coverage and Regen.
Kanto birds- Zapdos and Molres are just overall solid. Being able to both punish contact and lower PP at twice the rate is amazing in any metagame.
Amoongus- Absorbs T Spikes along with contact punishment and Regen, extremely nice often times.
Bronzong- Honestly just a worse Corviknight. No reliable recovery, no Defog, no Pressure or Mirror Armor, just completely outclassed. Don't get me wrong, it's solid, but there's little reason to use it when Corv exists except Trick Room teams.
Cinccino- 4MSS (4 moveslot syndrome) plus SIS (single item syndrome) along with being walled by every relevant steel type and being extremely heavily contact punished. I've called Cinccino a "noob bait" pokemon before and I stand by that. People think it will be all phenomenal until they start using it and realizing its huge weaknesses. Worn down by hazards, destroyed by contact punishment, not immune to any chip damage, ruined by status (mostly burn and para, but any other status is also tragic), Cinccino is much worse in practice than on paper.
Heracross- Guts+Moxie+Swarm. Gets itself into Swarm easier due to burn damage (Flame Orb is much better than Toxic Orb), hazards, and other forms of residual damage to increase the power of its already stupifying Megahorn. Not only that, but it gets stronger every time it knocks out an opposing pokemon. However, base 85 speed is just ok and Heracross has rather sub-par bulk.
Sigilyph- No need to run boots and it hits everything except 4x resists for neutral damage. However, can be reliant on setup with average bulk and mediocre special attack. Potentially devistating, but often nothing more than an inconvenience with status and Roost.
Machamp- Completely outclassed by both Conk and Heracross as guts fighting users. All Champ really has over them is 100% accurate moves. However, not even close to as devistating as the prior two mentioned pokemon. Even outclassed by Hariyama if it was in the gen 8 dex because Hariyama has both Thick Fat and Sheer Force along with Guts. Machamp's only accolades are not being worse than Throh as a Guts fighter and being better than Hariyama by default because Hariyama isn't in the gen 8 pokedex.
Mienshao- Not mentioned on the list, but I personally think it's around B+. Not completely outclassed by conk as its speed tier allows it to threatening to certain pokemon Conk can't threaten due to its low speed. Reckless making HJK 156 BP before items or stab means you have an absolutely insane stab attack to nuke the opposing pokemon with. Along with that, Mienshao can regain health with Regenerator and come back to wreak even more havoc. To add on to that, Mienshao can't even be Intimidated due to Inner Focus. Couple that with Knock for nice coverage and utility, U-Turn for momentum and recovery, Fake Out for chip damage and breaking Sturdy/Focus Sash, and extra coverage in Blaze Kick, Grass Knot, Acrobatics, Poison Jab, and Stone Edge, you receive an extreme threat. However, there is one main issue that holds it back, status vulnerability. Let's compare Mienshao to some of the A+ tier pokemon. Conk enjoys status as it increases its capability to bust through walls, Clefable and Reuniclus are immune residual damage from status, even if they don't appreciate paralysis taking some of their turns, and Dracozolt can be burned, but at least can't be slowed down and paralyzed due to its electric type. I think Mienshao will enjoy major rises in usage now that Mosa is gone as it now has more room to shine on teams and as a faster, but weaker, counterpart to Conk.