From my point of view, Gastly is a very important reason why the meta is overcentralized. Mienfoo and Vullaby are nearly mandatory on most good teams, in part because they're just that good into everything else too, but also in part because they're the only pivots that can both threaten all common Gastly sets (if tera isn't used) in a 1v1 when they're healthy, and be reliably good into the rest of the meta, unlike both Zorua and Elekid. Voltorb-hisui can also chip Gastly, but only if the Gastly is properly scouted to not be Choice Scarf. Gastly doesn't usually force otherwise bad Pokemon to be used, but it does make it much more difficult to use Pokemon such as Mareanie, Snubbull, Timburr, and Wattrel, limiting what types of teams can be effective into the meta. Other threats such as aforementioned Mienfoo and Vullaby, as well as Growlithe-Hisui and Shellder are also major pieces that limit team diversity, which is why this meta isn't as diverse as prior svlc metas. I support tiering action, even though there isn't a clear target that is near indisputably broken.
most teams boil down to Mienfoo + Vullaby + Vullaby switch in + 2 speed control/breaker slots, plus 1 of either another pivot, endgame wincon such as Shellder, or dedicated Mienfoo switch in. This format can be deviated from, but its difficult to make consistent and rarely has a distinct enough upside to be worth trying to do it. Hyper Offense can also be tried, but its generally inconsistent. There isn't a lot of room for creativity with which Pokemon you will use to glue a team together, especially as you must cover other threats such as Growlithe and Gastly with those slots too.
most teams boil down to Mienfoo + Vullaby + Vullaby switch in + 2 speed control/breaker slots, plus 1 of either another pivot, endgame wincon such as Shellder, or dedicated Mienfoo switch in. This format can be deviated from, but its difficult to make consistent and rarely has a distinct enough upside to be worth trying to do it. Hyper Offense can also be tried, but its generally inconsistent. There isn't a lot of room for creativity with which Pokemon you will use to glue a team together, especially as you must cover other threats such as Growlithe and Gastly with those slots too.