What I think about this team is that it doesn’t really have any direction. There’s no real strategy (that I can see) and in addition, lots of the Pokémon you’re using have better alternatives. Landorus-Therian is much better than its Incarnate form Nihilego, Terrakion and Coalossal are all better Rock Types than Lycanroc, and Charizard and Cinderace very much outclass Talonflame as Fire/flying types.
Rotom-W is okay, usually Regieleki and Tapu Fini outclass it but I think it's a good fit since you don't really have space for both, plus it is immune to earthquake from Landorus-T, which is some extra synergy. Wide Lens is interesting, but even with it you shouldn't be runnning thunder since it's still only 77% accurate. Most Rotoms will be Protect/Nasty plot/Hydro Pump/Thunderbolt + Sitrus Berry, which is good, but if you really want to use wide lens I'd use Electroweb over Thunderbolt because of the 95% accuracy and the speed control it offers, similar to Thunder Wave. You can also forgo Nasty Plot if you want thunderbolt as well.
Kartana is good but usually you'll want an Assault Vest on it. Aerial Ace is good coverage for max airstream.
Finally, Weavile. Weavile is usually outclassed by other things, but it is interesting in this case, especially since it hits a lot of things for super effective right now. Weavile has two gimmicky things you can do with it, both involving weakness policy.
The first Weavile strategy involves using A Weakness Policy Weavile paired with a life orb Dragapult. Dragapult uses infestation on Weavile, activating the weakness policy. Weavile’s pickpocket ability then steals Dragapult’s life orb, allowing it do do massive damage. (Note: I did not come up with this strategy, I saw it HERE.) The reason you’ll want to use Dragapult over Comfey (Draining Kiss) it a bullet punch user is that Dragapult learns Beat Up. As I mentioned, Terrakion is a better Rock Type than Lycanroc, and it had the ability justified. When you use beat up on a justified Pokémon, it will raise its attack to up to +4, making it do massive damage as well.
https://pokepast.es/97370a1c161b95df
The other thing you can do with Weavile is Beat Up + Weakness Policy activation for a partner. Weavile learns surf, which is used to activate the weakness policy of Pokémon like Cinderace and Coalossal. However, Dragapult and Whimsicott are both better at this task than Weavile, so if you want to use it, I’d stick to the first strategy. However, Whimsicott and Dragapult are both very good and would make your team strong.
For Dragapult, I’d use Terrakion and Cinderace as the Pokémon you’re supporting. You can use Coalossal as well, but then you'd have an extra slot to work with since it's both a Rock and Fire type. Another justified Pokemon could work, as well as just Urshifu. Urshifu-Single Strike is a great Late-Game Cleaner, but Rapid-Strike allows for aqua jet into Coalossal if you need priority to outspeed. If you use the Water form, change Rotom-W to Regieleki.
https://pokepast.es/220d7c5738bc9e43
Whimsicott doesn’t learn surf, but it does learn Sunny day, which pairs greatly with Charizard to allow it to do massive damage with Solar Power and Gmax Wildfire Additonally, Charizard is immune to earthquake, providing further synergy.
https://pokepast.es/7d26814acb27f08e
These are just 3 ideas I threw together based on your team's foundation, you can do a lot more with it (Coalossal, etc) but I hope this is a good starting point!
